Positive resist composition and method of pattern formation with the same

ABSTRACT

A positive resist composition comprising: (A) a resin which comes to have an enhanced solubility in an alkaline developing solution by an action of an acid; (B) a compound which generates an acid upon irradiation with actinic rays or a radiation; (C) a fluorine-containing compound containing at least one group selected from the groups (x) to (z); and (F) a solvent, and a method of pattern formation with the composition: (x) an alkali-soluble group; (y) a group which decomposes by an action of an alkaline developing solution to enhance a solubility in an alkaline developing solution; and (z) a group which decomposes by an action of an acid.

This is a Continuation application of U.S. application Ser. No.14/638,471 filed Mar. 4, 2015, which is a Continuation application ofU.S. application Ser. No. 13/345,978 filed Jan. 9, 2012 (now U.S. Pat.No. 9,057,952), which is a Continuation application of U.S. applicationSer. No. 11/492,123 filed Jul. 25, 2006 (now U.S. Pat. No. 8,871,421),which claims priority under 35 USC 119 from Japanese Application Nos.2005-215412 filed Jul. 26, 2005; 2005-356714 filed Dec. 9, 2005;2006-007762 filed Jan. 16, 2006; 2006-107727 filed Apr. 10, 2006; and2006-198897 filed Jul. 21, 2006, the disclosures of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a positive resist composition for usein lithographic steps in the production of semiconductors, e.g., IC's,in the production of circuit boards for liquid crystals, thermal heads,etc., and in other photofabrication processes, and further relates to amethod of pattern formation with the same. In particular, the inventionrelates to a positive resist composition suitable for exposure with animmersion type projection exposure apparatus employing far ultravioletrays having a wavelength of 300 nm or shorter as an exposure light, andto a method of pattern formation with the composition.

2. Description of the Related Art

With the trend toward size reduction in semiconductor elements, thewavelengths of exposure lights are decreasing and the numericalapertures (NA) of projection lenses are increasing. An exposureapparatus which has an NA of 0.84 and employs an ArF excimer laserhaving a wavelength of 193 nm as a light source has been developed sofar. As is generally well known, resolution and focal depth can beexpressed by the following equations:(Resolution)=k ₁·(λ/NA)(Focal depth)=±k ₂·λ/NA²

wherein λ is the wavelength of the exposure light, NA is the numericalaperture of the projection lens; and k₁ and k₂ are coefficients relatingto the process.

An exposure apparatus employing an F₂ excimer laser having a wavelengthof 157 nm as a light source is being investigated for the purpose ofenhancing resolution by using a shorter wavelength. However, use of thisapparatus is disadvantageous in that materials for the lens to be usedin the exposure apparatus and materials for resists are considerablylimited due to the use of such a shorter wavelength. Because of this,the cost of apparatus and material production is high and it isexceedingly difficult to stabilize quality. There is hence a possibilitythat an exposure apparatus and a resist which have sufficientperformances and stability might be not available in a desired period.

The so-called immersion method has been known as a technique forenhancing resolution in examinations with optical microscopes. In thismethod, the space between the projection lens and the sample is filledwith a liquid having a high refractive index (hereinafter referred toalso as “immersion liquid”).

This “immersion” has the following effects. In the immersion, theresolution and the focal depth can be expressed by the followingequations on the assumption that NA₀=sin θ:(Resolution)=k ₁·(λ₀ /n)/NA₀(Focal depth)=±k ₂·(λ₀ /n)/NA₀ ²wherein λ₀ is the wavelength of the exposure light in air; n is therefractive index of the immersion liquid relative to that of air; and θis the convergence half angle of the light.

Namely, the immersion produces the same effect as the use of an exposurelight having a wavelength reduced to 1/n. In other words, in the case ofan optical projection system having the same NA, the focal depth can beincreased to n times by the immersion. This is effective in all patternshapes and can be used in combination with a super resolution techniquesuch as the phase shift method or deformation illumination method whichis being investigated at present.

Examples of apparatus in which this effect is applied to the transfer offine image patterns for semiconductor elements are shown inJP-A-57-153433, JP-A-7-220990, etc.

Recent progress in the immersion exposure technique is reported in SPIEProc, 4688, 11(2002), J. Vac. Sci. Technol., B 17(1999), SPIE Proc.,3999, 2(2000), International Publication WO 2004-077158, pamphlet, etc.In the case where an ArF excimer laser is used as a light source, purewater (refractive index at 193 nm, 1.44) is thought to be most promisingfrom the standpoints of safety in handling and transmittance andrefractive index at 193 nm. Although solutions containing fluorine arebeing investigated for use in the case of using an F₂ excimer laser as alight source from the standpoint of a balance between transmittance andrefractive index at 157 nm, no immersion liquid has been found which issufficient from the standpoints of environmental safety and refractiveindex. In view of the degree of the effect of the immersion and thedegree of completion of resists, the technique of immersion exposure isthought to be employed first in ArF exposure apparatus.

Since the advent of resists for KrF excimer lasers (248 nm), thetechnique of image formation called chemical amplification has been usedas a resist image formation method for compensating for a sensitivitydecrease caused by light absorption. For example, the chemicalamplification type method for forming a positive image comprisesexposing a resist film to light to thereby cause an acid generator inthe exposed areas to decompose and generate an acid, subjecting theresist film to post-exposure bake (PEB) to utilize the resultant acid asa reaction catalyst to convert alkali-insoluble groups intoalkali-soluble groups, and removing the exposed areas by alkalidevelopment.

Resists for an ArF excimer laser (wavelength, 193 nm) which work by thechemical amplification mechanism are coming to be mainly used presently.However, use of these resists has a problem that a line pattern formedfalls to give defects in device production. An improvement in thisrespect has been desired.

It has been pointed out that application of a chemical amplificationtype resist to immersion exposure arouses troubles that since the resistlayer is in contact with an immersion liquid during exposure, the resistlayer alters and that components which exert an adverse influence on theimmersion liquid are released from the resist layer. InternationalPublication WO 2004-068242, pamphlet described an example in which aresist for ArF exposure changes in resist performance upon immersion inwater before and after exposure. It is pointed out therein that thischange is a problem in immersion exposure.

In the case where exposure in an immersion exposure process is conductedwith a scanning type immersion exposure machine, the immersion liquidshould follow the movement of the lens. However, in case where theimmersion liquid does not follow the lens, there is a fear that thespeed of exposure may decrease to influence productivity. When theimmersion liquid is water, the resist film desirably is hydrophobicbecause water on a hydrophobic resist film is more satisfactory infollowing-up properties. However, impartation of hydrophobicity to aresist film, on the other hand, results in adverse influences on theimage-forming performance of the resist, such as an increased scumamount. An improvement in this respect has been desired.

SUMMARY OF THE INVENTION

An object of the invention is to provide a positive resist compositionimproved in pattern profile and pattern falling and inhibited fromgenerating a scum. Other objects of the invention are to provide apositive resist composition which is satisfactory in the recedingcontact angle of an immersion liquid and is suitable also for immersionexposure and to provide a method of pattern formation with thiscomposition.

The invention provides a positive resist composition having thefollowing constitutions and a method of pattern formation with the same.Those objects of the invention are accomplished with these.

(1) A positive resist composition comprising:

(A) a resin which comes to have an enhanced solubility in an alkalinedeveloping solution by an action of an acid;

(B) a compound which generates an acid upon irradiation with actinicrays or a radiation;

(C) a fluorine-containing compound containing at least one groupselected from the groups (x) to (z):

-   -   (x) an alkali-soluble group;    -   (y) a group which decomposes by an action of an alkaline        developing solution to enhance a solubility in an alkaline        developing solution; and    -   (z) a group which decomposes by an action of an acid; and

(F) a solvent.

(2) The positive resist composition as described in (1) above,

wherein the fluorine-containing compound (C) is an alkali-solublecompound containing an alkyl group having a fluorine atom and 1 to 4carbon atoms, a cycloalkyl group having a fluorine atom or an aryl grouphaving a fluorine atom.

(3) The positive resist composition as described in (1) or (2) above,

wherein the fluorine-containing compound (C) has an alcoholic hydroxylgroup, and an alcohol moiety for the alcoholic hydroxyl group is afluorinated alcohol.

(4) The positive resist composition as described in any of (1) to (3)above,

wherein the fluorine-containing compound (C) has a structure representedby formula (F3):

wherein R₆₂ and R₆₃ each independently represents a fluoroalkyl group,provided that R₆₂ and R₆₃ may be bonded to each other to form a ring;and

R₆₄ represents a hydrogen atom, a fluorine atom or an alkyl group.

(5) The positive resin composition as described in any of (1) to (4)above,

wherein the group (y) which decomposes by an action of an alkalinedeveloping solution to enhance a solubility in an alkaline developingsolution has a lactone structure.

(6) The positive resist composition as described in any of (1) to (5)above,

wherein the fluorine-containing compound (C) is one of (C-1) to (C-13):

(C-1) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group; and    -   a repeating unit (X) containing an alkali-soluble group (x);

(C-2) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group; and    -   a repeating unit (Y) containing a group (y) decomposing by an        action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution;

(C-3) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group; and    -   a repeating unit (Z) containing a group (z) decomposing by an        action of an acid;

(C-4) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group;    -   a repeating unit (X) containing an alkali-soluble group (x); and    -   a repeating unit (Y) containing a group (y) decomposing by an        action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution;

(C-5) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group;    -   a repeating unit (X) containing an alkali-soluble group (x); and    -   a repeating unit (Z) containing a group (z) decomposing by an        action of an acid;

(C-6) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group;    -   a repeating unit (Y) containing a group (y) decomposing by an        action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution; and    -   a repeating unit (Z) containing a group (z) decomposing by an        action of an acid;

(C-7) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group;    -   a repeating unit (X) containing an alkali-soluble group (x);    -   a repeating unit (Y) containing a group (y) decomposing by an        action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution; and    -   a repeating unit (Z) containing a group (z) decomposing by an        action of an acid;

(C-8) a resin comprising:

-   -   a repeating unit (aX) containing both an alkali-soluble        group (x) and a fluoroalkyl group;

(C-9) a resin comprising:

-   -   a repeating unit (bY) containing both a group (y) decomposing by        an action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution and a fluoroalkyl        group;

(C-10) a resin comprising:

-   -   a repeating unit (aX) containing both an alkali-soluble        group (x) and a fluoroalkyl group having 1 to 4 carbon atoms;        and    -   a repeating unit (Y) containing a group (y) decomposing by an        action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution;

(C-11) a resin comprising:

-   -   a repeating unit (aX) containing both an alkali-soluble        group (x) and a fluoroalkyl group; and    -   a repeating unit (Z) containing a group (z) decomposing by an        action of an acid;

(C-12) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group; and,    -   a repeating unit (aX) containing both an alkali-soluble        group (x) and a fluoroalkyl group; and

(C-13) a resin comprising:

-   -   a repeating unit (a) having a fluoroalkyl group; and    -   a repeating unit (aY) containing both a group (y) decomposing by        an action of an alkaline developing solution to enhance a        solubility in an alkaline developing solution and a fluoroalkyl        group.

(7) The positive resist composition as described in any of (1) to (6)above,

wherein the fluorine-containing compound (C) has a molecular weight offrom 1,000 to 100,000.

(8) The positive resist composition as described in any of (1) to (7)above,

wherein an amount of the fluorine-containing compound (C) added is from0.1 to 5% by mass.

(9) The positive resist composition as described in any of (1) to (8)above, which provides a film with which water has a receding contactangle of 65° or larger.

(10) The positive resist composition as described in any of (1) to (9)above, which provides a film with which water has a receding contactangle of 70° or larger.

(11) The positive resist composition as described in any of (1) to (10)above,

wherein the resin (A) contains a repeating unit having a polycyclichydrocarbon group substituted by a hydroxyl group or a cyano group.

(12) The positive resist composition as described in any of (1) to (11)above,

wherein the resin (A) is a copolymer comprising at least threecomponents: a (meth)acrylate repeating unit having a lactone ring; a(meth)acrylate repeating unit having an organic group having at leastone of a hydroxyl group and a cyano group; and a (meth)acrylaterepeating unit having an acid-decomposable group.

(13) The positive resist composition as described in any of (1) to (12)above,

wherein the resin (A) has no fluorine atom.

(14) The positive resist composition as described in any of (1) to (13)above,

wherein the compound (B) which generates an acid upon irradiation withactinic rays or a radiation is a compound which generates an acid havinga fluoroalkyl chain or a benzenesulfonic acid having a fluorine atomupon irradiation with actinic rays.

(15) The positive resist composition as described in any of (1) to (14)above,

wherein the compound (B) which generates an acid upon irradiation withactinic rays or a radiation is a triphenylsulfonium salt compound havingan alkyl or cycloalkyl residue which has not been substituted byfluorine in a cation part.

(16) The positive resist composition as described in any of (1) to (15)above,

wherein the solvent (F) is a mixed solvent comprising two or moresolvents including propylene glycol monomethyl ether acetate.

(17) The positive resist composition as described in any of (1) to (16)above, which further comprises at least one of a fluorochemicalsurfactant and a silicone surfactant.

(18) The positive resist composition as described in any of (1) to (17)above, which has a total solid concentration of from 1.0 to 6.0% bymass.

(19) A method of pattern formation, which comprises:

forming a resist film from a positive resist composition as described inany of (1) to (18) above;

exposing the resist film to light; and

developing the resist film.

(20) The method of pattern formation as described in (19) above,

wherein the resist film is exposed to light having a wavelength of from1 to 200 nm.

(21) The method of pattern formation as described in (19) or (20) above,

wherein the exposure is immersion exposure in which the resist film isexposed to light through an immersion liquid.

(22) A resin having structures represented by formulae (CI) to (CIII):

wherein X represents a hydrogen atom, a halogen atom or an alkyl group;

Rf represents an alkyl group having a fluorine atom, a cycloalkyl grouphaving a fluorine atom or an aryl group having a fluorine atom;

Y represents an alkylene group, a di-valent connecting group having analicyclic hydrocarbon structure, a single bond, an ether group, an estergroup, a carbonyl group, a carboxyl group or a di-valent group obtainedby these groups;

V represents a group having a lactone ring;

Rc represents an unsubstituted hydrocarbon group, provided that Rc doesnot contain a hetero-atom; and

m, n and p each represents a numeral satisfying following relationships:m+n+p=100, 0<m<100, 0<n<100 and 0≦p<100.

(23) A resin having structures represented by formulae (CI), (CIV) and(CIII):

wherein X represents a hydrogen atom, a halogen atom or an alkyl group;

Rf represents an alkyl group having a fluorine atom, a cycloalkyl grouphaving a fluorine atom or an aryl group having a fluorine atom;

Y represents an alkylene group, a di-valent connecting group having analicyclic hydrocarbon structure, a single bond, an ether group, an estergroup, a carbonyl group, a carboxyl group or a di-valent group obtainedby these groups;

Rp₁ represents a group which decomposes by an action of an acid;

Rc represents an unsubstituted hydrocarbon group, provided that Rc doesnot contain a hetero-atom; and

m, n and p each represents a numeral satisfying following relationships:m+n+p=100, 0<m<100, 0<n<100 and 0≦p<100.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view showing a receding contact angle;

FIG. 2 is a diagrammatic view illustrating the state in which thewater's property of following up a quartz plate is being evaluated; and

FIG. 3A to 3D are diagrammatic views illustrating the water's propertyof following up a quartz plate.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be explained below in detail.

With respect to expressions of groups (atomic groups) in thisspecification, the expressions which include no statement as to whetherthe groups are substituted or unsubstituted imply both of groups havingno substituents and groups having one or more substituents. For example,the term “alkyl group” implies not only an alkyl group having nosubstituents (unsubstituted alkyl group) but also an alkyl group havingone or more substituents (substituted alkyl group).

(A) Resin Coming to Have Enhanced Solubility in Alkaline DevelopingSolution by Action of Acid

The resist composition of the invention contains a resin whichdecomposes by the action of an acid to come to have enhanced solubilityin an alkaline developing solution (acid-decomposable resin). This resinis one in which the main chain or side chains thereof or both the mainchain and side chains thereof have groups (hereinafter referred to alsoas “acid-decomposable groups”) which decompose by the action of an acidto generate alkali-soluble groups (this resin is hereinafter referred toalso as “resin (A)”). The resin (A) preferably is analicyclic-hydrocarbon-based acid-decomposable resin having an alicyclichydrocarbon structure which is monocyclic or polycyclic.

Examples of the alkali-soluble groups include phenolic hydroxyl,carboxy, fluorinated alcohol, sulfo, sulfonamide, sulfanilamide,(alkylsulfonyl)(alkylcarbonyl)methylene,(alkylsulfonyl)(alkylcarbonyl)imide, bis(alkylcarbonyl)methylene,bis(alkylcarbonyl)imide, bis(alkylsulfonyl)methylene,bis(alkylsulfonyl)imide, and tris(alkylcarbonyl)methylene groups andgroups having a tris(alkylsulfonyl)methylene group.

Preferred examples of the alkali-soluble groups include carboxy,fluorinated alcohol (preferably hexafluoroisopropanol), and sulfogroups.

The groups decomposable with an acid (acid-decomposable groups)preferably are those alkali-soluble groups in which the hydrogen atomhas been replaced by a group eliminable with an acid.

Preferred examples of the acid-decomposable groups include cumyl ester,enol ester, acetal ester, and tertiary alkyl ester groups. Morepreferred are tertiary alkyl ester groups.

The resin (A) preferably is a resin containing at least one kind ofrepeating units selected from the group consisting of repeating unitshaving a partial structure which includes an alicyclic hydrocarbon andis represented by any of the following general formulae (pI) to (pV) andrepeating units represented by the following general formula (II-AB).

In general formulae (pI) to (pV),

R₁₁ represents methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, orsec-butyl, and Z represents an atomic group necessary for forming acycloalkyl group in cooperation with the carbon atom.

R₁₂ to R₁₆ each independently represents a linear or branched alkylgroup having 1-4 carbon atoms or a cycloalkyl group, provided that atleast one of R₁₂ to R₁₄ or either of R₁₅ and R₁₆ represents a cycloalkylgroup.

R₁₇ to R₂₁ each independently represents a hydrogen atom, a linear orbranched alkyl group having 1-4 carbon atoms, or a cycloalkyl group,provided that at least one of R₁₇ to R₂₁ represents a cycloalkyl groupand that either of R₁₉ and R₂₁ represents a linear or branched alkylgroup having 1-4 carbon atoms or a cycloalkyl group.

R₂₂ to R₂₅ each independently represents a hydrogen atom, a linear orbranched alkyl group having 1-4 carbon atoms, or a cycloalkyl group,provided that at least one of R₂₂ to R₂₅ represents a cycloalkyl groupand that R₂₃ and R₂₄ may be bonded to each other to form a ring.

In formula (II-AB),

R₁₁′ and R₁₂′ each independently represents a hydrogen atom, cyano,halogen atom, or alkyl group.

Z′ represents an atomic group which forms an alicyclic structure incooperation with the two carbon atoms (C—C) bonded thereto.

General formula (II-AB) preferably is the following general formula(II-AB1) or general formula (II-AB2).

In formulae (II-AB1) and (II-AB2),

R₁₃′ to R₁₆′ each independently represents a hydrogen atom, halogenatom, cyano, —COOH, —COOR₅, group which decomposes by the action of anacid, —C(═O)—X-A′-R₁₇′, alkyl group, or cycloalkyl group,

wherein R₅ represents an alkyl group, cycloalkyl group, or group havinga lactone structure,

X represents an oxygen atom, sulfur atom, —NH—, —NHSO₂—, or —NHSO₂NH—,and

A′ represents a single bond or a divalent connecting group,

provided that at least two of R₁₃′ to R₁₆ ′ may be bonded to each otherform a ring.

Symbol n represents 0 or 1.

R₁₇′ represents —COOH, —COOR₅, —CN, hydroxy, alkoxy, —CO—NH—R₆,—CO—NH—SO₂—R₆, or group having a lactone structure.

R₆ represents an alkyl group or a cycloalkyl group.

In general formulae (pI) to (pV), the alkyl groups represented by R₁₂ toR₂₅ are linear or branched alkyl groups having 1-4 carbon atoms.

The cycloalkyl groups represented by R₁₁ to R₂₅ and the cycloalkyl groupformed by Z and a carbon atom may be monocyclic or polycyclic. Examplesthereof include groups having a monocyclic, bicyclic, tricyclic, ortetracyclic structure having 5 or more carbon atoms, preferably 6-30carbon atoms, especially preferably 7-25 carbon atoms. These cycloalkylgroups may have substituents.

Preferred examples of the cycloalkyl groups include adamantyl,noradamantyl, decalin residues, tricyclodecanyl, tetracyclododecanyl,norbornyl, cedrol, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl,cyclodecanyl, and cyclododecanyl. More preferred examples thereofinclude adamantyl, norbornyl, cyclohexyl, cyclopentyl,tetracyclododecanyl, and tricyclodecanyl.

Those alkyl and cycloalkyl groups may have substituents. Examples of thesubstituents which may be optionally possessed include alkyl groups(having 1-4 carbon atoms), halogen atoms, hydroxyl, alkoxy groups(having 1-4 carbon atoms), carboxyl, and alkoxycarbonyl groups (having2-6 carbon atoms). These alkyl, alkoxy, alkoxycarbonyl groups and thelike may have substituents, examples of which include hydroxyl, halogenatoms, and alkoxy groups.

The structures represented by general formulae (pI) to (pV) in the resincan be used for the protection of the alkali-soluble groups.

Repeating units having an alkali-soluble group protected by a structurerepresented by any of general formulae (pI) to (pV) preferably arerepeating units represented by the following general formula (pA).

In general formula (pA),

R represents a hydrogen atom, a halogen atom, or a linear or branchedalkyl group having 1-4 carbon atoms. The R's may be the same ordifferent.

Symbol A represents one member or a combination of two or more membersselected from the group consisting of a single bond and alkylene, ether,thioether, carbonyl, ester, amide, sulfonamide, urethane, and ureagroups. Preferably, A is a single bond.

Rp₁ represents a group represented by any of formulae (pI) to (pV).

The repeating units represented by general formula (pA) most preferablyare repeating units derived from a 2-alkyl-2-adamantyl (meth)acrylate ora dialkyl(1-adamantyl)methyl (meth)acrylate.

Specific examples of the repeating units represented by general formula(pA) are shown below.

(In the formulae, Rx is H, CH₃, CF₃, or CH₂OH, and Rxa and Rxb each arean alkyl group having 1-4 carbon atoms.)

(In the formulae, Rx is H, CH₃, CF₃, or CH₂OH, and Rxa and Rxb each arean alkyl group having 1-4 carbon atoms.)

Examples of the halogen atoms represented by R₁₁′ and R₁₂′ includechlorine, bromine, fluorine, and iodine atoms.

Examples of the alkyl groups represented by R₁₁′ and R₁₂′ include linearor branched alkyl groups having 1-10 carbon atoms.

The atomic group represented by Z′, which is for forming an alicyclicstructure, is an atomic group which serves to form, in the resin,repeating units of an alicyclic hydrocarbon which may have one or moresubstituents. Especially preferred is an atomic group for forming abridged alicyclic structure forming repeating units of a bridgedalicyclic hydrocarbon.

Examples of the framework of the alicyclic hydrocarbon to be formedinclude the same frameworks as those of the alicyclic hydrocarbon groupsrepresented by R₁₁ to R₂₅ in general formulae (pI) to (pV).

The framework of the alicyclic hydrocarbon may have one or moresubstituents.

Examples of the substituents include R₁₃′ to R₁₆′ in general formula(II-AB1) or (II-AB2).

In the resin (A) according to the invention, groups decomposing by theaction of an acid can be contained in at least one kind of repeatingunits selected from: repeating units having a partial structure whichincludes an alicyclic hydrocarbon and is represented by any of generalformulae (pI) to (pV); repeating units represented by general formula(II-AB); and repeating units derived from the comonomer components whichwill be described later.

Various substituents of R₁₃′ to R₁₆′ in general formula (II-AB1) or(II-AB2) can serve as substituents of the atomic group for forming analicyclic structure in general formula (II-AB) or of the atomic group Zfor forming a bridged alicyclic structure.

Specific examples of the repeating units represented by general formula(II-AB1) or (II-AB2) include the following. However, the repeating unitsin the invention should not be construed as being limited to thefollowing examples.

The resin (A) in the invention preferably has groups having a lactonering. The groups having a lactone ring may be any groups having alactone ring. However, preferred examples thereof are groups having a 5-to 7-membered lactone structure and ones comprising a 5- to 7-memberedlactone structure and another ring structure fused thereto so as to forma bicycle structure or spiro structure. More preferred are groups havinga lactone structure represented by any of the following general formulae(LC1-1) to (LC1-16). Groups having a lactone structure may have beendirectly bonded to the main chain. Preferred lactone structures are(LC1-1), (LC1-4), (LC1-5), (LC1-6), (LC1-13), and (LC1-14). Use of alactone structure brings about satisfactory results concerning line edgeroughness and development defects.

The lactone structure parts may have one or more substituents (Rb₂) orhave no substituents. Preferred examples of the substituents (Rb₂)include alkyl groups having 1-8 carbon atoms, cycloalkyl groups having4-7 carbon atoms, alkoxy groups having 1-8 carbon atoms, alkoxycarbonylgroups having 1-8 carbon atoms, carboxyl, halogen atoms, hydroxyl,cyano, and acid-decomposable groups. Symbol n2 represents an integer of0-4. When n2 is 2 or larger, the Rb₂'s may be the same or different andmay be bonded to each other to form a ring.

Examples of repeating units having a group having a lactone structurerepresented by any of general formulae (LC1-1) to (LC1-16) include:repeating units represented by general formula (II-AB1) or (II-AB2)wherein at least one of R₁₃′ to R₁₆′ has a group represented by any ofgeneral formulae (LC1-1) to (LC1-16) (e.g., the repeating units whichhave —COOR₅ wherein R₅ is represented by any of general formulae (LC1-1)to (LC1-16)); and repeating units represented by the following generalformula (AI).

In general formula (AI),

Rb₀ represents a hydrogen atom, halogen atom, or alkyl group having 1-4carbon atoms. Preferred examples of substituents which may be possessedby the alkyl group represented by Rb₀ include hydroxyl and halogenatoms.

Examples of the halogen atom represented by Rb₀ include fluorine,chlorine, bromine, and iodine atoms. Rb₀ preferably is a hydrogen atomor methyl.

Ab represents an alkylene group, a divalent connecting group having amonocyclic or polycyclic, alicyclic hydrocarbon structure, a singlebond, an ether, ester, carbonyl, or carboxyl group, or a divalent groupcomprising a combination of two or more of these. Preferably, Ab is asingle bond or a connecting group represented by -Ab₁-CO₂—.

Ab₁ is a linear or branched alkylene group or a monocyclic or polycycliccycloalkylene group, and preferably is methylene, ethylene,cyclohexylene, adamantylene, or norbornylene group.

V represents a group represented by any of general formulae (LC1-1) to(LC1-16).

Repeating units having a lactone structure generally have opticalisomers, and any of these optical isomers may be used. One opticalisomer may be used alone, or a mixture of two or more optical isomersmay be used. In the case where one optical isomer is mainly used, it hasan optical purity (ee) of preferably 90 or higher, more preferably 95 orhigher.

Specific examples of the repeating units having a lactone structure areshown below, but the repeating units in the invention should not beconstrued as being limited to the following examples.

(In the formulae, Rx is H, CH₃, CH₂OH, or CF₃.)

(In the formulae, Rx is H, CH₃, CH₂OH, or CF₃.)

(In the formulae, Rx is H, CH₃, CH₂OH, or CF₃.)

The resin (A) in the invention preferably contains repeating unitshaving an alicyclic hydrocarbon structure substituted by one or morepolar groups. The presence of these repeating units improves adhesion tosubstrates and affinity for developing solutions. The polar groupspreferably are hydroxyl and cyano.

More preferably, the resin (A) contains repeating units having apolycyclic hydrocarbon group substituted by one or more hydroxyl orcyano groups.

Preferred examples of the alicyclic hydrocarbon structure substituted byone or more polar groups include structures represented by generalformulae (VIIa) and (VIIb).

In general formula (VIIa), R_(2c) to R_(4c) each independentlyrepresents a hydrogen atom, hydroxyl, or cyano, provided that at leastone of R_(2c) to R_(4c) represents hydroxyl or cyano. Preferably, one ortwo of R_(2c) to R_(4c) are hydroxyl and the remaining two or more is ahydrogen atom. More preferably, two of R_(2c) to R_(4c) are hydroxyl andthe remaining one is a hydrogen atom.

The groups represented by general formula (VIIIa) or (VIIb) preferablyare dihydroxy groups or monohydroxy groups, and more preferably aredihydroxy groups.

Examples of repeating units having a group represented by generalformula (VIIa) or (VIIb)) include: repeating units represented bygeneral formula (II-AB1) or (II-AB2) wherein at least one of R₁₃′ toR₁₆′ has a group represented by general formula (VIIa) or (VIIb) (e.g.,the repeating units which have —COOR₅ wherein R₅ is a group representedby general formula (VIIa) or (VIIb)); and repeating units represented bythe following general formula (AIIa) to (AIId).

In general formulae (AIIa) to (AIId),

R_(1c) represents a hydrogen atom, methyl, trifluoromethyl, orhydroxymethyl.

R_(2c) to R_(4c) each independently represents a hydrogen atom,hydroxyl, or cyano, provided that at least one of R_(2c) to R_(4c)represents hydroxyl or cyano. Preferably, one or two of R_(2c) to R_(4c)are hydroxyl and the remaining two or more is a hydrogen atom. Morepreferably, two of R_(2c) to R_(4c) are hydroxyl and the remaining oneis a hydrogen atom.

Specific examples of the repeating units represented by general formulae(AIIa) to (AIId) are shown below, but the repeating units in theinvention should not be construed as being limited to the followingexamples.

The resin (A) in the invention may contain repeating units representedby the following general formula (VIII).

In general formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ representsa hydrogen atom, hydroxyl, alkyl group, or —OSO₂—R₄₂. R₄₂ represents analkyl group, cycloalkyl group, or camphor residue. The alkyl grouprepresented by R₄₁ or R₄₂ may be substituted by a halogen atom(preferably fluorine atom), etc.

Specific examples of the repeating units represented by general formula(VIII) include the following, but the repeating units in the inventionshould not be construed as being limited to these examples.

The resin (A) in the invention preferably has repeating units eachhaving an alkali-soluble group, and more preferably has repeating unitseach having a carboxyl group. The presence of these repeating unitsenhances resolution in contact hole applications. The repeating unitshaving a carboxyl group may be either repeating units which constitute aresin main chain having carboxyl groups directly bonded thereto, such asthe repeating units derived from acrylic acid or methacrylic acid, orrepeating units which constitute a resin main chain having carboxylgroups each bonded thereto through a connecting group. Both of these twotypes of repeating units are preferred. The connecting group may have amonocyclic or polycyclic hydrocarbon structure. Most preferred arerepeating units derived from acrylic acid or methacrylic acid.

The resin (A) in the invention may further have repeating units having1-3 groups represented by general formula (F1). The presence of theserepeating units improves line edge roughness performance.

In general formula (F1), R₅₀ to R₅₅ each independently represents ahydrogen atom, fluorine atom, or alkyl group, provided that at least oneof R₅₀ to R₅₅ represents a fluorine atom or an alkyl group in which atleast one hydrogen atom has been replaced by a fluorine atom(fluoroalkyl group). Rx represents a hydrogen atom or an organic group(preferably, an acid-decomposable protective group or an alkyl,cycloalkyl, acyl, or alkoxycarbonyl group).

The alkyl groups represented by R₅₀ to R₅₅ may have been substituted byone or more substituents selected from halogen atoms, e.g., fluorine,cyano, etc. Preferred examples thereof include alkyl groups having 1-3carbon atoms, such as methyl and trifluoromethyl. It is preferred thatR₅₀ to R₅₅ each be a fluorine atom.

Preferred examples of the organic group represented by Rx includeacid-decomposable protective groups and alkyl, cycloalkyl, acyl,alkylcarbonyl, alkoxycarbonyl, alkoxycarbonylmethyl, alkoxymethyl, and1-alkoxyethyl groups which may have one or more substituents.

The repeating units having 1-3 groups represented by general formula(F1) preferably are repeating units represented by the following generalformula (F2).

In formula (F2), Rx represents a hydrogen atom, halogen atom, or alkylgroup having 1-4 carbon atoms. The alkyl group represented by Rx mayhave one or more substituents, and preferred examples of thesubstituents include hydroxyl and halogen atoms.

Fa represents a single bond or a linear or branched alkylene group, andpreferably represents a single bond.

Fb represents a monocyclic or polycyclic hydrocarbon group.

Fc represents a single bond or a linear or branched alkylene group(preferably represents a single bond or methylene group).

F₁ represents a group represented by general formula (F1).

Symbol p₁ represents 1-3.

Preferred examples of the cyclic hydrocarbon group represented by Fbinclude cyclopentyl, cyclohexyl, and norbornyl.

Specific examples of the repeating units having 1-3 structuresrepresented by general formula (F1) are shown below.

The resin (A) in the invention may further have repeating units whichhave an alicyclic hydrocarbon structure and are not acid-decomposable.The presence of these repeating units is effective in inhibitinglow-molecular components contained in the resist film from dissolving inthe immersion liquid during immersion exposure. Examples of suchrepeating units including units derived from 1-adamantyl (meth)acrylate,tricyclodecanyl (meth)acrylate, and cyclohexyl (meth)acrylate.

From the standpoint of compatibility, it is preferred that the resin (A)has no fluorine atom.

The resin (A) in the invention can contain various repeating structuralunits besides the repeating structural units described above for thepurpose of regulating dry etching resistance, suitability for standarddeveloping solutions, adhesion to substrates, resist profile, andgeneral properties required of resists, such as resolution, heatresistance, sensitivity, etc.

Examples of such repeating structural units include the repeatingstructural units corresponding to the monomers shown below, but theoptional units should not be construed as being limited to these.

Thus, performances required of the resin (A), in particular, (1)solubility in solvent for application, (2) film-forming properties(glass transition point), (3) alkali developability, (4) resist loss(hydrophilicity/hydrophobicity, selection of alkali-soluble group), (5)adhesion of unexposed areas to substrate, (6) dry etching resistance,and the like can be delicately regulated.

Examples of such monomers include compounds having oneaddition-polymerizable unsaturated bond, such as acrylic esters,methacrylic esters, acrylamide and analogues thereof, methacrylamide andanalogues thereof, allyl compounds, vinyl ethers, and vinyl esters.

Besides such monomers corresponding to those various repeatingstructural units, any addition-polymerizable unsaturated compoundcopolymerizable with those monomers may have been copolymerized.

In the resin (A), the molar proportion of each kind of repeatingstructural units to be contained is suitably determined in order toregulate resist properties including dry etching resistance, suitabilityfor standard developing solutions, adhesion to substrates, and resistprofile and general performances required of resists, such asresolution, heat resistance, and sensitivity.

Preferred embodiments of the resin (A) in the invention include thefollowing.

-   (1) One containing repeating units having a partial structure which    includes an alicyclic hydrocarbon and is represented by any of    general formulae (pI) to (pV) (side chain type). This embodiment    preferably is one containing (meth)acrylate repeating units having a    structure represented by any of (pI) to (pV).-   (2) One containing repeating units represented by general formula    (II-AB) (main chain type), provided that examples of the resin (2)    include the following.-   (3) One comprising repeating units represented by general formula    (II-AB), a maleic anhydride derivative, and a (meth)acrylate    structure (hybrid type).

In the resin (A), the content of the repeating units having anacid-decomposable group is preferably 10-60% by mole, more preferably20-50% by mole, even more preferably 25-40% by mole, based on allrepeating structural units.

In the resin (A), the content of the repeating units having a partialstructure which includes an alicyclic hydrocarbon and is represented byany of general formulae (pI) to (pV) is preferably 25-70% by mole, morepreferably 35-65% by mole, even more preferably 40-60% by mole, based onall repeating structural units.

In the resin (A), the content of the repeating units represented bygeneral formula (II-AB) is preferably 10-70% by mole, more preferably15-65% by mole, even more preferably 25-60% by mole, based on allrepeating structural units.

The content of the repeating structural units derived from thoseoptionally usable comonomers in the resin also can be suitablydetermined according to the desired resist performances. In general,however, the content thereof is preferably 99% by mole or lower, morepreferably 90% by mole or lower, even more preferably 80% by mole orlower, based on the total amount of the repeating structural unitshaving a partial structure which includes an alicyclic hydrocarbon andis represented by any of general formulae (pI) to (pV) and the repeatingunits represented by general formula (II-AB).

In the case where the composition of the invention is to be used for ArFexposure, the resin preferably has no aromatic group from the standpointof transparency to ArF light.

The resin (A) preferably is a copolymer of three components, i.e., a(meth)acrylate having a lactone ring, a (meth)acrylate having an organicgroup having at least either of hydroxyl and cyano, and a (meth)acrylatehaving an acid-decomposable group.

More preferably, the resin (A) to be used in the invention is one inwhich all the repeating units are constituted of (meth)acrylaterepeating units. In this case, the resin to be use can be any of one inwhich all the repeating units are methacrylate units, one in which allthe repeating units are acrylate units, and one in which the repeatingunits are a mixture of methacrylate units and acrylate units. It is,however, preferred that the proportion of acrylate repeating units is upto 50 mol % based on all repeating units. The resin more preferably is:a terpolymer comprising 25-50% repeating units having a partialstructure which includes an alicyclic hydrocarbon and is represented byany of general formulae (pI) to (pV), 25-50% repeating units having thelactone structure, and 5-30% repeating units having an alicyclichydrocarbon structure substituted by the polar group; or a quadripolymercontaining, besides these three kinds of repeating units, 5-20%repeating units containing a carboxyl group or a structure representedby general formula (F1).

The polymer or copolymer to be used in the invention has aweight-average molecular weight in the range of preferably1,500-100,000, more preferably 2,000-70,000, especially preferably3,000-50,000.

The resin (A) to be used in the invention can be synthesized by ordinarymethods (e.g., radical polymerization). Examples of general synthesismethods include the en bloc polymerization method in which monomers andan initiator are dissolved in a solvent and the solution is heated tothereby polymerize the monomers and the dropping polymerization methodin which a solution of monomers and an initiator is added dropwise to aheated solvent over 1-10 hours. The dropping polymerization method ispreferred. Examples of the reaction solvent include ethers such astetrahydrofuran, 1,4-dioxane, and diisopropyl ether, ketones such asmethyl ethyl ketone and methyl isobutyl ketone, ester solvents such asethyl acetate, amide solvents such as dimethylformamide anddimethylacetamide, and solvents capable of dissolving the composition ofthe invention therein, such as those which will be shown later, e.g.,propylene glycol monomethyl ether acetate, propylene glycol monomethylether, and cyclohexanone. It is more preferred that polymerization beconducted using the same solvent as that to be used in the resistcomposition of the invention. Use of this solvent can inhibit particlegeneration during storage.

It is preferred that the polymerization reaction be conducted in aninert gas atmosphere such as nitrogen or argon. A commercialfree-radical initiator (e.g., azo initiator or peroxide) is used as apolymerization initiator to initiate the polymerization. Thefree-radical initiator preferably is an azo initiator, which preferablyis an azo initiator having an ester group, cyano group, or carboxylgroup. Preferred initiators include azobisisobutyronitrile,azobisdimethylvaleronitrile, and dimethyl2,2′-azobis(2-methylpropionate). The initiator may be added additionallyor in portions according to need. After completion of the reaction, thereaction mixture is poured into a solvent and the target polymer isrecovered as a powder, solid, etc. The reactant concentration is 5-50%by mass, preferably 10-30% by mass. (In this specification, mass ratiois equal to weight ratio.) The reaction temperature is generally 10-150°C., preferably 30-120° C., more preferably 50-100° C.

In the invention, the amount of the resin (A) added to thephotosensitive composition is 50-99.7% by mass, preferably 70-99.5% bymass, based on all solid components. Besides the resin according to theinvention, other resins may be used according to need. Other resins canbe incorporated into the composition of the invention preferably in sucha proportion that the amount thereof per 100 parts by mass of the resin(A) in the invention is up to 70 parts by mass, especially preferably upto 50 parts by mass.

(B) Compound Generating Acid upon Irradiation with Actinic Ray orRadiation

The photosensitive composition of the invention contains a compoundwhich generates an acid upon irradiation with actinic rays or aradiation (referred to also as component (B) or compound (B)).

The photo-acid generator to be used can be suitably selected fromphotoinitiators for cationic photopolymerization, photoinitiators forradical photopolymerization, photodecolorants or optical color changersfor dyes, known compounds used in microresist formation or the likewhich generate an acid upon irradiation with actinic rays or aradiation, and mixtures of two or more thereof.

Examples thereof include diazonium salts, phosphonium salts, sulfoniumsalts, iodonium salts, imidesulfonates, oximesulfonates,diazodisulfones, disulfones, and o-nitrobenzyl sulfonates.

Also usable are compounds obtained by incorporating any of those groupsor compounds which generate an acid upon irradiation with actinic raysor a radiation into the main chain or side chains of a polymer. Examplesthereof are given in, e.g., U.S. Pat. No. 3,849,137, German Patent3,914,407, JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038,JP-A-63-163452, JP-A-62-153853, and JP-A-63-146029.

Furthermore, those compounds generating an acid by the action of lightwhich are described in U.S. Pat. No. 3,779,778, European Patent 126,712,etc. can be used.

Component (B) preferably is a compound which, upon irradiation withactinic rays, generates an acid having one or more fluoroalkyl chains(preferably having 2-4 carbon atoms) or a benzenesulfonic acid havingone or more fluorine atoms.

Furthermore, component (B) preferably is a triphenylsulfonium saltcompound having in the cation part either an alkyl residue (preferablyhaving 1-15 carbon atoms) which has not been substituted by fluorine ora cycloalkyl residue (preferably having 3-15 carbon atoms) which has notbeen substituted by fluorine.

Preferred of the compounds which decompose upon irradiation with actinicrays or a radiation to generate an acid are compounds represented by thefollowing general formulae (ZI), (ZII), and (ZIII).

In general formula (ZI), R₂₀₁, R₂₀₂, and R₂₀₃ each independentlyrepresents an organic group.

X⁻ represents a non-nucleophilic anion. Preferred examples thereofinclude a sulfonic acid anion, carboxylic acid anion,bis(alkylsulfonyl)amide anion, tris(alkylsulfonyl)methide anion, BF₄ ⁻,PF₆ ⁻, and SbF₆ ⁻. Preferred are organic anions containing one or morecarbon atoms.

Preferred examples of the organic anions include organic anionsrepresented by the following formulae.

In the formulae, Rc₁ represents an organic group.

Examples of the organic group represented by Rc₁ include ones having1-30 carbon atoms. Preferred examples thereof include alkyl and arylgroups which may have one or more substituents, and further includegroups comprising two or more of these groups connected to each otherthrough a single bond or a connecting group such as —O—, —CO₂—, —S—,—SO₃—, or —SO₂N(Rd₁)-. Rd₁ represents a hydrogen atom or alkyl group.

Rc₃, Rc₄, and Rc₅ each represent an organic group. Preferred examples ofthe organic groups represented by Rc₃, Rc₄, and Rc₅ include the sameorganic groups as those shown above as preferred examples of Rb₁. Mostpreferred are perfluoroalkyl groups having 1-4 carbon atoms.

Rc₃ and Rc₄ may be bonded to each other to form a ring.

Examples of the group formed by the bonding of Rc₃ and Rc₄ includealkylene groups and arylene groups. Preferred are perfluoroalkylenegroups having 2-4 carbon atoms.

Most preferred examples of the organic groups represented by Rc₁ and Rc₃to Rc₅ are: alkyl groups substituted in the 1-position by a fluorineatom or fluoroalkyl group; and a phenyl group substituted by one or morefluorine atoms or fluoroalkyl groups. The presence of one or morefluorine atoms or fluoroalkyl groups enables the acid generated by lightirradiation to have an increased acidity to improve sensitivity.Furthermore, the formation of a ring by the bonding of Rc₃ and Rc₄enables the acid generated by light irradiation to have an increasedacidity to improve sensitivity.

The number of carbon atoms in each of the organic groups represented byR₂₀₁, R₂₀₂, and R₂₀₃ is generally 1-30, preferably 1-20.

Two of R₂₀₁ to R₂₀₃ may be bonded to each other to form a ringstructure, which may contain an oxygen atom, sulfur atom, ester bond,amide bond, or carbonyl group therein.

Examples of the group formed by the bonding of two of R₂₀₁ to R₂₀₃include alkylene groups (e.g., butylene and pentylene).

Examples of the organic groups represented by R₂₀₁, R₂₀₂, and R₂₀₃include the corresponding groups in the compounds (Z1-1), (Z1-2), and(Z1-3) which will be described later.

A compound having two or more structures represented by general formula(ZI) may also be used. For example, use may be made of a compound havinga structure in which at least one of the R₂₀₁ to R₂₀₃ of a compoundrepresented by general formula (ZI) is bonded to at least one of theR₂₀₁ to R₂₀₃ of another compound represented by general formula (ZI).

More preferred examples of the component (ZI) include the compounds(Z1-1), (Z1-2), and (Z1-3) which will be explained below.

Compound (Z1-1) is an arylsulfonium compound represented by generalformula (ZI) wherein at least one of R₂₀₁ to R₂₀₃ is an aryl group,i.e., a compound including an arylsulfonium as a cation.

The arylsulfonium compound may be one in which all of R₂₀₁ to R₂₀₃ arearyl groups, or may be one in which part of R₂₀₁ to R₂₀₃ is an arylgroup and the remainder is an alkyl group.

Examples of the arylsulfonium compound include triarylsulfoniumcompounds, diarylalkylsulfonium compounds, and aryldialkylsulfoniumcompounds.

The aryl group of the arylsulfonium compound preferably is an aryl groupsuch as phenyl or naphthyl or a heteroaryl group such as an indoleresidue or pyrrole residue, and more preferably is phenyl or an indoleresidue. In the case where the arylsulfonium compound has two or morearyl groups, these aryl groups may be the same or different.

The alkyl group which is optionally possessed by the arylsulfoniumcompound preferably is a linear, branched, or cyclic alkyl group having1-15 carbon atoms. Examples thereof include methyl, ethyl, propyl,n-butyl, sec-butyl, t-butyl, cyclopropyl, cyclobutyl, and cyclohexyl.

The aryl and alkyl groups represented by R₂₀₁ to R₂₀₃ may havesubstituents selected from alkyl groups (e.g., ones having 1-15 carbonatoms), aryl groups (e.g., ones having 6-14 carbon atoms), alkoxy groups(e.g., ones having 1-15 carbon atoms), halogen atoms, hydroxyl, andphenylthio. Preferred examples of the substituents are linear, branched,or cyclic alkyl groups having 1-12 carbon atoms and linear, branched, orcyclic alkoxy groups having 1-12 carbon atoms. Most preferred are alkylgroups having 1-4 carbon atoms and alkoxy groups having 1-4 carbonatoms. Any one of R₂₀₁ to R₂₀₃ may have such a substituent or each ofR₂₀₁ to R₂₀₃ may have such a substituent. In the case where R₂₀₁ to R₂₀₃are aryl groups, it is preferred that a substituent be bonded to thep-position in each aryl group.

Next, compound (Z1-2) will be explained.

Compound (Z1-2) is a compound represented by formula (ZI) wherein R₂₀₁to R₂₀₃ each independently represents an organic group containing noaromatic ring. The term aromatic ring herein implies any of aromaticrings including ones containing one or more heteroatoms.

The organic groups containing no aromatic ring which are represented byR₂₀₁ to R₂₀₃ each have generally 1-30, preferably 1-20 carbon atoms.

Preferably, R₂₀₁ to R₂₀₃ each independently are an alkyl, 2-oxoalkyl,alkoxycarbonylmethyl, allyl, or vinyl group. R₂₀₁ to R₂₀₃ each morepreferably are a linear, branched, or cyclic 2-oxoalkyl oralkoxycarbonylmethyl group, and most preferably are a linear or branched2-oxoalkyl group.

The alkyl groups represented by R₂₀₁ to R₂₀₃ may be either linear,branched, or cyclic. Preferred examples thereof include linear orbranched alkyl groups having 1-10 carbon atoms (e.g., methyl, ethyl,propyl, butyl, and pentyl) and cycloalkyl groups having 3-10 carbonatoms (e.g., cyclopentyl, cyclohexyl, and norbomyl).

The 2-oxoalkyl groups represented by R₂₀₁ to R₂₀₃ may be either linear,branched, or cyclic. Preferred examples thereof include the alkyl groupsenumerated above which each have >C═O in the 2-position.

Examples of the alkyl groups in the alkoxycarbonylmethyl groupsrepresented by R₂₀₁ to R₂₀₃ include alkoxy groups preferably having 1-5carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy group,and pentoxy group).

R₂₀₁ to R₂₀₃ may have been further substituted by substituents selectedfrom halogen atoms, alkoxy groups (e.g., ones having 1-5 carbon atoms),hydroxyl, cyano, and nitro.

Two of R₂₀₁ to R₂₀₃ may be bonded to each other to form a ringstructure, which may contain an oxygen atom, sulfur atom, ester bond,amide bond, or carbonyl group therein. Examples of the group formed bythe bonding of two of R₂₀₁ to R₂₀₃ include alkylene groups (e.g.,butylene and pentylene).

Compound (Z1-3) is a compound represented by the following generalformula (Z1-3). Namely, it is a compound having a phenacylsulfonium saltstructure.

R_(1C) to R_(5C) each independently represents a hydrogen atom, alkyl oralkoxy group, or halogen atom.

R_(6C) and R_(7C) each represent a hydrogen atom or an alkyl group.

R_(x) and R_(y) each independently represents an alkyl, 2-oxoalkyl,alkoxycarbonylmethyl, allyl, or vinyl group.

Two or more of R_(1C) to R_(5C) may be bonded to each other to form aring structure, and R_(x) and R_(y) may be bonded to each other to forma ring structure. These ring structures may contain an oxygen atom,sulfur atom, ester bond, or amide bond.

The alkyl groups represented by R_(1C) to R_(5C) may be either linear,branched, or cyclic. Examples thereof include alkyl groups having 1-20carbon atoms, preferably, linear or branched alkyl groups having 1-12carbon atoms (e.g., methyl, ethyl, linear or branched propyl, linear orbranched butyl, and linear or branched pentyl), and cycloalkyl groupshaving 3-8 carbon atoms (e.g., cyclopentyl and cyclohexyl).

The alkoxy groups represented by R_(1C) to R_(5C) may be either linear,branched, or cyclic. Examples thereof include alkoxy groups having 1-10carbon atoms. Preferred examples thereof include linear or branchedalkoxy groups having 1-5 carbon atoms (e.g., methoxy, ethoxy, linear orbranched propoxy, linear or branched butoxy, and linear or branchedpentoxy) and cyclic alkoxy groups having 3-8 carbon atoms (e.g.,cyclopentyloxy and cyclohexyloxy).

It is preferred that any of R_(1C) to R_(5C) be a linear, branched, orcyclic alkyl group or a linear, branched, or cyclic alkoxy group. It ismore preferred that the total number of carbon atoms in R_(1C) to R_(5C)be from 2 to 15. This compound has further improved solubility insolvents and is inhibited from generating particles during storage.

Examples of the alkyl groups represented by R_(x) and R_(y) include thesame alkyl groups as those enumerated above as examples of R_(1C) toR_(5C).

Examples of the 2-oxoalkyl groups include those alkyl groups representedby R_(1C) to R_(5C) which each have >C═O in the 2-position.

Examples of the alkoxy groups in the alkoxycarbonylmethyl groups includethe same alkoxy groups as those enumerated above as examples of R_(1C)to R_(5C).

Examples of the group formed by the bonding of R_(x) and R_(y) includebutylene and pentylene.

R_(x) and R_(y) each preferably are an alkyl group having 4 or morecarbon atoms, and more preferably are an alkyl group having 6 or more,especially 8 or more carbon atoms.

In general formulae (ZII) and (ZIII), R₂₀₄ to R₂₀₇ each independentlyrepresents an aryl group which may have one or more substituents or analkyl group which may have one or more substituents.

The aryl groups represented by R₂₀₄ to R₂₀₇ preferably are phenyl ornaphthyl, and more preferably are phenyl.

The alkyl groups represented by R₂₀₄ to R₂₀₇ may be either linear,branched, or cyclic. Preferred examples thereof include linear orbranched alkyl groups having 1-10 carbon atoms (e.g., methyl, ethyl,propyl, butyl, and pentyl) and cycloalkyl groups having 3-10 carbon atom(e.g., cyclopentyl, cyclohexyl, and norbornyl).

Examples of substituents which may be possessed by R₂₀₄ to R₂₀₇ includealkyl groups (e.g., ones having 1-15 carbon atoms), aryl groups (e.g.,ones having 6-15 carbon atoms), alkoxy groups (e.g., ones having 1-15carbon atoms), halogen atoms, hydroxyl, and phenylthio.

X⁻ represents a non-nucleophilic anion, and examples thereof include thesame non-nucleophilic anions as those enumerated above as examples ofthe X⁻ in general formula (I).

Other preferred examples of the compound which decomposes uponirradiation with actinic rays or a radiation to generate an acid includecompounds represented by the following general formulae (ZIV), (ZV), and(ZVI).

In general formulae (ZIV) to (ZVI), Ar₃ and Ar₄ each independentlyrepresents an aryl group.

R₂₀₆ represents an alkyl group or a substituted or unsubstituted arylgroup. R₂₀₇ and R₂₀₈ each independently represents an alkyl or arylgroup or an electron-attracting group. R₂₀₇ preferably is an aryl group.

R₂₀₈ preferably is an electron-attracting group, and more preferably iscyano or a fluoroalkyl group.

Symbol A represents an alkylene, alkenylene, or arylene group.

More preferred of the compounds which decompose upon irradiation withactinic rays or a radiation to generate an acid are the compoundsrepresented by general formulae (ZI) to (ZIII).

Especially preferred examples of the compounds which decompose uponirradiation with actinic rays or a radiation to generate an acid areshown below.

One acid generator can be used alone, or a combination of two or moreacid generators can be used. In the case where two or more acidgenerators are used in combination, it is preferred to use a combinationof compounds respectively generating two organic acids differing in thetotal number of atoms excluding hydrogen atoms by 2 or more.

The content of the acid generator in the composition is preferably0.1-20% by mass, more preferably 0.5-10% by mass, even more preferably1-7% by mass, based on all solid components of the resist composition.

(C) Fluorine-Containing Compound

The positive resin composition of the invention contains afluorine-containing compound containing at least one group selected fromthe following groups (x) to (z):

(x) alkali-soluble groups;

(y) groups which decompose by the action of an alkaline developingsolution to enhance solubility in the alkaline developing solution; and

(z) groups which decompose by the action of an acid.

Examples of the alkali-soluble groups (x) include phenolic hydroxyl,carboxy, fluorinated alcohol, sulfo, sulfonamide, sulfonylimide,(alkylsulfonyl)(alkylcarbonyl)methylene,(alkylsulfonyl)(alkylcarbonyl)imide, bis(alkylcarbonyl)methylene,bis(alkylcarbonyl)imide, bis(alkylsulfonyl)methylene,bis(alkylsulfonyl)imide, and tris(alkylcarbonyl)methylene groups andgroups having a tris(alkylsulfonyl)methylene group.

Preferred examples of the alkali-soluble groups include fluorinatedalcohol (preferably hexafluoroisopropanol) sulfonimide, andbis(alkylcarbonyl)methylene groups.

In the case where the fluorine-containing compound (C) is a resin,preferred repeating units having an alkali-soluble group (x) arerepeating units each having an alkali-soluble group directly bonded tothe main chain of the resin, such as repeating units derived fromacrylic acid or methacrylic acid, and repeating units each having analkali-soluble group bonded to the main chain of the resin through aconnecting group. Also preferred is to use a polymerization initiator orchain-transfer agent having an alkali-soluble group in polymerization tointroduce the alkali-soluble group into a polymer end.

The content of the repeating units having an alkali-soluble group (x) ispreferably 1-50 mol %, more preferably 3-35 mol %, even more preferably5-20 mol %, based on all repeating units in the polymer.

Specific examples of the repeating units having an alkali-soluble group(x) are shown below.

(In the formulae, Rx is H, CH₃, CF₃, or CH₂OH.)

Examples of the groups (y) which decompose by the action of an alkalinedeveloping solution to enhance solubility in the alkaline developingsolution include groups having a lactone structure, acid anhydrides, andacid imide groups. Preferred are lactone groups.

In the case where the fluorine-containing compound (C) is a resin,preferred repeating units having a group (y) decomposing by the actionof an alkaline developing solution to enhance solubility in the alkalinedeveloping solution are repeating units each having a group enhancingsolubility in an alkaline developing solution bonded to the main chainof the resin through a connecting group, such as repeating units derivedfrom an acrylic ester or methacrylic ester. It also preferred that apolymerization initiator or chain-transfer agent having a group (y)enhancing solubility in an alkaline developing solution be used inpolymerization to introduce the group into a polymer end.

The content of the repeating units having a group (y) enhancingsolubility in an alkaline developing solution is preferably 1-40 mol %,more preferably 3-30 mol %, even more preferably 5-15 mol %, based onall repeating units in the polymer.

Specific examples of the repeating units having a group (y) enhancingsolubility in an alkaline developing solution include the same lactonestructures and structures represented by general formula (VIII) as thoseshown above with regard to the resin (A).

Examples of the groups (z) which decompose by the action of an acidinclude the same acid-decomposable groups as those enumerated above withregard to the resin (A). In the case where the fluorine-containingcompound (C) is a resin, examples of repeating units containing a group(z) decomposing by the action of an acid include the same repeatingunits as those containing an acid-decomposable group which were shownabove with regard to the resin (A). When the fluorine-containingcompound (C) is a resin, the content of the repeating units having agroup (z) decomposing by the action of an acid is preferably 1-80 mol %,more preferably 10-80 mol %, even more preferably 20-60 mol %, based onall repeating units in the polymer.

In the fluorine-containing compound (C), the fluorine atoms may becontained in the groups (x) to (z) or in other parts. In the case wherethe fluorine-containing compound (C) is a resin, the fluorine atoms maybe contained in the main chain of the resin or in side chains thereof.Preferably, the fluorine atoms are contained in side chains. Thefluorine atoms may be contained in the repeating units containing any ofthe groups (x) to (z) or may be contained in other repeating units.

It is preferred that the fluorine-containing compound (C) be a compoundcontaining an alkyl group having one or more fluorine atoms (fluoroalkylgroup) (preferably having 1-4 carbon atoms), a cycloalkyl group havingone or more fluorine atoms, or an aryl group having one or more fluorineatoms.

The alkyl group having one or more fluorine atoms is a linear orbranched alkyl group substituted by at least one fluorine atom. Thisgroup may have other substituents.

The cycloalkyl group having at least one fluorine atom is a monocyclicor polycyclic cycloalkyl group substituted by at least one fluorineatom. This group may have other substituents.

Examples of the aryl group having at least one fluorine atom includearyl groups, such as phenyl and naphthyl, which have been substituted byat least one fluorine atom. This group may have other substituents.

The alkyl group having one or more fluorine atoms, cycloalkyl grouphaving one or more fluorine atoms, and aryl group having one or morefluorine atoms preferably have any of structures represented by thefollowing general formulae (F1) to (F3).

In general formulae (F1) to (F3),

R₅₀ to R₆₄ each independently represents a hydrogen atom, fluorine atom,or alkyl group,

provided that at least one of R₅₀ to R₅₅, at least one of R₅₇ to R₆₁,and at least one of R₆₂ to R₆₄ each represent a fluorine atom or analkyl group in which at least one hydrogen atom has been replaced by afluorine atom (i.e., a fluoroalkyl group, which preferably has 1-4carbon atoms).

It is preferred that all of R₅₀ to R₅₅ and R₅₇ to R₆₁ be fluorine atoms.

R₆₂ to R₆₃ each preferably are a fluoroalkyl group having 1-4 carbonatoms, and more preferably are a perfluoroalkyl group having 1-4 carbonatoms.

R₆₂ and R₆₃ may be bonded to each other to form a ring.

Examples of the structure represented by general formula (F1) include—CF₂OH, —C(CF₃)₂OH, —C(C₂F₅)₂OH, —C(CF₃)(CH₃)OH, and —CH(CF₃)OH. Thestructure preferably is —C(CF₃)₂OH.

Examples of the structure represented by general formula (F2) includep-fluorobenzene, pentafluorobenzene, and 3,5-di(trifluoromethyl)benzene.

Examples of the structure represented by general formula (F3) includetrifluoroethyl, pentafluoropropyl, pentafluoroethyl, heptafluorobutyl,hexafluoroisopropyl, heptafluoroisopropyl,hexafluoro(2-methyl)isopropyl, nonafluorobutyl, octafluoroisobutyl,nonafluorohexyl, nonafluoro-t-butyl, perfluoroisopentyl, perfluorooctyl,perfluoro(trimethyl)hexyl, 2,2,3,3-tetrafluorocyclobutyl, andperfluorocyclohexyl. The structure preferably is hexafluoroisopropyl,heptafluoroisopropyl, hexafluoro(2-methyl)isopropyl, octafluoroisobutyl,nonafluoro-t-butyl, or perfluoroisopentyl, and more preferably ishexafluoroisopropyl or heptafluoroisopropyl.

The compound (C) preferably is any of the following resins (C-1) to(C-13). More preferably, it is any of resins (C-1) to (C-4) and (C-8) to(C-13).

(C-1)

A resin comprising

repeating units (a) having a fluoroalkyl group and

repeating units (X) containing an alkali-soluble group (x).

This resin more preferably is a copolymer resin consisting only ofrepeating units (a) and repeating units (X).

(C-2)

A resin comprising

repeating units (a) having a fluoroalkyl group and

repeating units (Y) containing a group (y) decomposing by the action ofan alkaline developing solution to enhance solubility in the alkalinedeveloping solution.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a) and repeating units (Y).

(C-3)

A resin comprising

repeating units (a) having a fluoroalkyl group and

repeating units (Z) containing a group (z) decomposing by the action ofan acid.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a) and repeating units (Z).

(C-4)

A resin comprising

repeating units (a) having a fluoroalkyl group,

repeating units (X) containing an alkali-soluble group (x), and

repeating units (Y) containing a group (y) decomposing by the action ofan alkaline developing solution to enhance solubility in the alkalinedeveloping solution.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a), repeating units (X), and repeating units (Y).

(C-5)

A resin comprising

repeating units (a) having a fluoroalkyl group,

repeating units (X) containing an alkali-soluble group (x), and

repeating units (Z) containing a group (z) decomposing by the action ofan acid.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a), repeating units (X), and repeating units (Z).

(C-6)

A resin comprising

repeating units (a) having a fluoroalkyl group,

repeating units (Y) containing a group (y) decomposing by the action ofan alkaline developing solution to enhance solubility in the alkalinedeveloping solution, and

repeating units (Z) containing a group (z) decomposing by the action ofan acid.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a), repeating units (Y), and repeating units (Z).

(C-7)

a resin comprising

repeating units (a) having a fluoroalkyl group,

repeating units (X) containing an alkali-soluble group (x),

repeating units (Y) containing a group (y) decomposing by the action ofan alkaline developing solution to enhance solubility in the alkalinedeveloping solution, and

repeating units (Z) containing a group (z) decomposing by the action ofan acid.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a), repeating units (X), repeating units (Y), andrepeating units (Z).

(C-8)

A resin comprising

repeating units (aX) containing both an alkali-soluble group (x) and afluoroalkyl group.

This resin more preferably is a resin (homopolymer) consisting only ofrepeating units (aX).

(C-9)

A resin comprising

repeating units (bY) containing both a group (y) decomposing by theaction of an alkaline developing solution to enhance solubility in thealkaline developing solution and a fluoroalkyl group.

This resin more preferably is a resin (homopolymer) consisting only ofrepeating units (bY).

(C-10)

A resin comprising

repeating units (aX) containing both an alkali-soluble group (x) and afluoroalkyl group having 1-4 carbon atoms and

repeating units (Y) containing a group (y) decomposing by the action ofan alkaline developing solution to enhance solubility in the alkalinedeveloping solution.

This resin more preferably is a copolymer resin consisting only ofrepeating units (aX) and repeating units (Y).

(C-11)

A resin comprising

repeating units (aX) containing both an alkali-soluble group (x) and afluoroalkyl group and

repeating units (Z) containing a group (z) decomposing by the action ofan acid.

This resin more preferably is a copolymer resin consisting only ofrepeating units (aX) and repeating units (Z).

(C-12)

A resin comprising

repeating units (a) having a fluoroalkyl group and

repeating units (aX) containing both an alkali-soluble group (x) and afluoroalkyl group.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a) and repeating units (aX).

(C-13)

A resin comprising

repeating units (a) having a fluoroalkyl group and

repeating units (aY) containing both a group (y) decomposing by theaction of an alkaline developing solution to enhance solubility in thealkaline developing solution and a fluoroalkyl group.

This resin more preferably is a copolymer resin consisting only ofrepeating units (a) and repeating units (aY).

In such copolymers, the repeating unit (a) having a fluoroalkyl grouppreferably does not contain any alkali-soluble group.

In resins (C-1), (C-2), and (C-4), the amount of repeating units (a)incorporated is preferably 40-99% by mole, more preferably 60-80% bymole.

In resin (C-10), the amount of repeating units (aX) incorporated ispreferably 40-99% by mole, more preferably 60-90% by mole.

Specific examples of repeating units having one or more fluorine atomsinclude repeating units represented by formulae (C1) to (C8), which willbe described later. Specific examples of repeating units (aX) includerepeating units (C1) and (C2), which will be described later. Inparticular, as specific examples of the repeating unit (a), therepeating unit represented by (C4) to (C7) to be described later can bementioned for example, specifically including the following ones.

As the repeating unit (aX), the repeating units (C1) and (C2) can bementioned for example, specifically including the following ones.

As the repeating unit (aY), those (C3), which will be described later,are mentioned as examples.

The fluorine-containing compound (C) in the invention can containvarious repeating structural units, besides the repeating units (C1) to(C8) which will be described later, for the purpose of regulatingfilm-forming properties, applicability, compatibility, and recedingcontact angle.

Examples of such repeating units include units derived from a compoundhaving one or more addition-polymerizable unsaturated bonds which isselected from acrylic esters, methacrylic esters, acrylamide andderivatives thereof, methacrylamide and derivatives thereof, styrene andderivatives thereof, allyl compounds, vinyl ethers, vinyl esters, andthe like. Preferably, the compound is an acrylic or methacrylic esterhaving a branched alkyl group having 6-20 carbon atoms or a cycloalkylgroup having 6-20 carbon atoms, acrylamide or a derivative thereof,methacrylamide or a derivative thereof, or styrene which may have analkyl group having 1-10 carbon atoms.

Furthermore, any addition-polymerizable unsaturated compoundcopolymerizable with the monomers corresponding to those variousrepeating structural units may have been copolymerized.

Specific examples of the fluorine-containing compound (C) include resinscontaining repeating units represented by any of the following generalformulae (C1) to (C8).

In general formulae (C1) to (C8),

Rf's each independently represents a group having a fluoroalkyl group(preferably having 1-4 carbon atoms).

P represents a linear or branched alkylene group or a monocyclic orpolycyclic cycloalkylene group, and preferably is methylene, ethylene,cyclohexylene, adamantylene, or norbronylene.

X's each independently represents a hydrogen atom, halogen atom, oralkyl group. The alkyl group may be linear or branched and may have oneor more substituents, e.g., halogen atoms.

Q's each independently represents a single bond, an alkylene group, adivalent group having a monocyclic or polycyclic alicyclic hydrocarbonstructure, an ether, ester, or carbonyl group, or a divalent groupcomprising a combination of two or more of these, provided that informula (C1), when n is 2 or 3, then Q represents any of those divalentgroups substituted by one or two groups represented by —C(Rf)₂—OH. Qpreferably is a single bond or a connecting group represented by-Q₁-CO₂—. Q₁ is a linear or branched alkylene group or a monocyclic orpolycyclic cycloalkylene group, and preferably is methylene, ethylene,cyclohexylene, adamantylene, or norbornylene.

Symbol n's each independently represents a natural number of 1-3.

X₁₁ represents an oxygen atom or a group represented by —N(R₁₃)—. R₁₃represents a hydrogen atom, linear or branched alkyl group (preferablyhaving 1-20 carbon atoms), or cycloalkyl group (preferably having up to20 carbon atoms).

R₁₁'s each independently represents a hydrogen atom, halogen atom, oralkyl group. The alkyl group may be linear or branched and may have oneor more substituents, e.g., halogen atoms.

R₁₂ and R₂₁ to R₂₃ each independently represents an organic group havingat least one fluorine atom.

P₂ represents an alicyclic group.

R₂₀ represents an organic group.

R₄ to R₇ each represent a hydrogen atom, a fluorine atom, a linear orbranched alkyl group having 1-4 carbon atoms, or a linear or branchedfluoroalkyl group having 1-4 carbon atoms, provided that at least one ofR₄ to R₇ represents a fluorine atom and that R₄ and R₅ or R₆ and R₇ mayform a ring.

Preferred examples of the repeating units having one or more fluorineatoms, in the case where the fluorine-containing compound has a highmolecular weight (resin), are shown below, but the repeating unitsshould not be construed as being limited to the following examples.

Specific examples of the fluorine-containing compound having a highmolecular weight (resin) are shown below, but the compound should not beconstrued as being limited to the following examples.

In the case where the fluorine-containing compound (C) is analkali-soluble compound, the amount of the alkali-soluble groups (acidgroups) is preferably 0.1-10 meq/g, more preferably 0.1-3 meq/g, evenmore preferably 0.1-2 meq/g, in terms of the acid value of thealkali-soluble compound (C). The acid value means the amount (mg) ofpotassium hydroxide required for neutralizing the compound.

The fluorine-containing compound (C) contains fluorine atoms in anamount of preferably 5-80% by mass, more preferably 10-80% by mass, evenmore preferably 20-60% by mass, based on the molecular weight of thefluorine-containing compound (C).

Although the fluorine-containing compound (C) may be either alow-molecular compound or a high-molecular compound (e.g., a resin), itpreferably is a high-molecular compound in view of the trouble thatlow-molecular components are released from a resist into an immersionliquid to foul the lens. The molecular weight thereof is preferably1,000-100,000, more preferably 1,000-50,000, even more preferably1,500-15,000.

In the case where the fluorine-containing compound (C) is a resin, theamount of residual monomers therein is preferably 0-10% by mass, morepreferably 0-5% by mass, even more preferably 0-1% by mass. From thestandpoints of resolution, resist shape, resist pattern side walls,roughness, etc., use is made of a resin having a molecular-weightdistribution (Mw/Mn; referred to also as dispersity ratio) in the rangeof preferably 1-5, more preferably 1-3, even more preferably 1-1.5.

The amount of the fluorine-containing compound (C) added to the positiveresist composition is preferably 0.1-30% by mass, more preferably0.1-10% by mass, even more preferably 0.1-5% by mass, based on all solidcomponents of the resist composition.

One fluorine-containing compound (C) may be used alone, or a mixture oftwo or more fluorine-containing compounds (C) may be used.

The fluorine-containing compound (C) to be used can be any of variouscommercial products or can be synthesized by an ordinary method. Forexample, in the case where the compound (C) is a resin, it can beobtained through, e.g., radical polymerization such as that for thesynthesis of the acid-decomposable resin (A) described above and generalpurification, etc.

It is a matter of course that the fluorine-containing compound (C) isreduced in the content of impurities such as metals like the resin (A)containing acid-dissociable groups. In addition, when the compound (C)is a high-molecular compound, it is preferred that the amount ofresidual monomers and oligomer components is not larger than apredetermined value, e.g., 0.1% by mass in terms of HPLC value. Thus,not only the composition can give a resist further improved insensitivity, resolution, process stability, pattern shape, etc., butalso a resist is obtained which is not causative of foreign-mattergeneration in the liquid and does not change with time in sensitivity,etc.

Fluorine-containing compound (C) is preferably the following resin (C1)or (C2), too.

The resin (C1) has the structure represented by the following formula.

In formulae (CI) to (CIII);

X each independently represents a hydrogen atom, a halogen atom or analkyl group, which may be of straight-chain or branched, or further mayhave a substituent group such as a halogen atom;

Rf each independently represents a fluorine-containing alkyl grouphaving a straight-chain or branched alkyl group substituted with atleast one fluorine atom, preferably being one represented by theaforementioned general formula (F2) or (F3).

Y represents an alkylene group, a di-valent connecting group having analicyclic hydrocarbon structure (monocyclic or polycyclic), a singlebond, an ether group, an ester group, a carboxyl group or a carboxylgroup, or a di-valent group combining these groups. Among these, asingle bond is preferred.

V represents a group having a lactone ring, preferably representing thegroup represented by one of the general formulae (LC1-1) to (LC1-16) forthe aforementioned resin (A).

Rc each independently represents an unsubstituted hydrocarbon group,provided that Rc does not contain a hetero atom such as oxygen orhalogen. Specifically, Rc represents a branched alkyl group, acycloalkyl group, a branched alkenyl group, a cycloalkenyl group or anaryl group. Preferably Rc has 4 to 20 carbon atoms, more preferably 7 to15, whereby it may be of straight-chain, branched or cyclic, butpreferably branched or cyclic.

m, n and p each represents a number satisfying the followingrelationship. m+n+p=100, 0<m<100, 0<n<100 and 0≦p<100; preferably m isfrom 20 to 80, n is from 20 to 60, and p is from 0 to 50, and morepreferably m is from 20 to 80, n is from 20 to 40 and p is from 10 to50.

The resin (C2) has the structure represented by the following formula.

In formulae (CI), (CIV) and (CIII), X, Rf, Y and Rc are the same asthose in the aforementioned (CI) to (CIII).

Rp₁ represents a group which decomposes by the action of an acid.

m, n and p each represents a number satisfying the followingrelationship.

m+n+p=100, 0<m<100, 0<n<100 and 0≦p<100.

Preferably m is 10 to 90, n is 10 to 90 and p is 0 to 50, and morepreferably m is 20 to 80, n is 20 to 80 and p is 10 to 50.

In the following, specific preferable examples for the repeating unitrepresented by general formula (CI) are shown, but the repeating unitshould not be construed as being limited thereto.

As the repeating unit represented by general formula (CII), those forthe repeating unit having a lactone structure in the aforementionedresin (A) can be specifically mentioned.

In the following, preferable specific examples for the repeating unitrepresented by general formula (CIII) are shown, but the repeating unitshould not be construed as being limited thereto.

As the group which decomposes by the action of an acid in generalformula (CIV), for example, —C(R₃₆)(R₃₇)(R₃₈) and —CH₂(OR₃₉) can bementioned.

R₃₆ to R₃₉ each independently represent an alkyl group, a cycloalkylgroup, an aryl group, an aralkyl group or an alkenyl group. R₃₆ and R₃₇may combine together to form a ring.

The alkyl group for R₃₆ to R₃₉ preferably has 1 to 10 carbon atoms,i.e., representing, for example, methyl, ethyl, propyl, n-butyl,sec-butyl, hexyl or octyl.

The cycloalkyl group for R₃₆ to R₃₉ may be monocyclic or polycyclic. Asa monocyclic group, cycloalkyl groups with 3 to 8 carbon atoms arepreferred, i.e., representing, for example, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl or cyclooctyl. As a polycyclic group, cycloalkylgroups with 6 to 20 carbon atoms are preferred, representing, forexample, adamantyl, norbornyl, isobornyl, camphanyl, dicyclopentyl,α-pinenyl, tricyclodecanyl, tetracyclododecyl or androstanyl.

The aryl group for R₃₆ to R₃₉ preferably has 6 to 10 carbon atoms,representing, for example, phenyl, naphthyl or anthryl.

The aralkyl group for R₃₆ to R₃₉ preferably has 7 to 12 carbon atoms,representing, for example, benzyl, phenetyl or naphtylmethyl.

The alkenyl group for R₃₆ to R₃₉ preferably has 2 to 8 carbon atoms,representing, for example, vinyl, allyl, butenyl or cyclohexenyl.

In the following, specific preferable examples for the repeating unitrepresented by general formula (CIV) are shown, but the repeating unitshould not be construed as being limited thereto.

(In the formulae, Rx represents H or CH₃, Rxa and Rxc each represent analkyl group with 1 to 4 carbon atoms.)

The resin (C1) and (C2) can be synthesized by ordinary methods (e.g.,radical polymerization). Examples of general synthesis methods includethe en bloc polymerization method in which monomers and an initiator aredissolved in a solvent and the solution is heated to thereby polymerizethe monomers and the dropping polymerization method in which a solutionof monomers and an initiator is added dropwise to a heated solvent over1-10 hours. The dropping polymerization method is preferred. Examples ofthe reaction solvent include ethers such as tetrahydrofuran,1,4-dioxane, and diisopropyl ether, ketones such as methyl ethyl ketoneand methyl isobutyl ketone, ester solvents such as ethyl acetate, amidesolvents such as dimethylformamide and dimethylacetamide, and solventscapable of dissolving the composition of the invention therein, such asthose which will be shown later, e.g., propylene glycol monomethyl etheracetate, propylene glycol monomethyl ether and cyclohexanone. It is morepreferred that polymerization be conducted using the same solvent asthat to be used in the resist composition of the invention. Use of thissolvent can suppress particle generation during storage.

It is preferred that the polymerization reaction be conducted in aninert gas atmosphere such as nitrogen or argon. A commercially availableradical initiator (e.g., azo initiator or peroxide) is used as apolymerization initiator to initiate the polymerization. The radicalinitiator preferably is an azo initiator, which preferably is an azoinitiator having an ester group, cyano group, or carboxyl group.Preferred initiators include azobisisobutyronitrile,azobisdimethylvaleronitrile, and dimethyl2,2′-azobis(2-methylpropionate). The initiator may be added additionallyor in portions according to need.

The reaction temperature is generally 10-150° C., preferably 30-120° C.,more preferably 50-100° C.

After completion of the reaction, the reaction mixture is left forcooling and subjected to purification operation. As the purificationoperation, those ordinarily in use can be adopted, includingpurification methods under solution state such as liquid-liquidextraction method which removes the residual monomers or oligomercomponents by rinsing with water or combining suitable solvents, andultrafiltration which extracts and removes ingredients having molecularweights below a specified value, and those under solid state such as thereprecipitation method that removes residual monomers by coagulating theresin in a poor solvent, and one based on rinsing the filtered resinslurry with a poor solvent. For example, the resin is separated as asolid by bringing a solvent in which the aforementioned resin issparingly soluble or difficult to solve (a poor solvent) in a volumeamount ten times or less (preferably in a volume amount ten to fivetimes) of that of the reaction solution into contact with the reactionsolution.

As the solvent used for the precipitation or reprecipitation operationfrom a polymer solution (precipitation or reprecipitation solvent), anyone can be used so long as it is a poor solvent for the polymer.Depending on the type of polymer, there may be used according toappropriate choice, for example, hydrocarbons (aliphatic hydrocarbonssuch as pentane, hexane, heptane or octane; alicyclic hydrocarbons suchas cyclohexane or methylcyclohexane; aromatic hydrocarbons such asbenzene, toluene or xylene; halogenated aliphatic hydrocarbons such ashalogenated hydrocarbons (methylene chloride, chloroform or carbontetrachloride; halogenated aromatic hydrocarbons such as chlorobenzeneor dichlorobenzene), nitro compounds (nitromethane or nitgroethane),nitriles (acetonitrile or benzonitrile), ethers (chain-type ethers suchas diethyl ether, diisopropyl ether or dimethoxyethane; cyclic etherssuch as tetrahydrofuran or dioxane), esters (ethyl acetate or butylacetate), carbonates (dimethyl carbonate, diethyl carbonate, ethylenecarbonate or propylene carbonate), alcohols (methanol, ethanol,propanol, isopropyl alcohol or butanol), carboxylic acids (acetic acid),water, and mixed solvents containing these. Among these, as aprecipitation or reprecipitation solvent, those containing at least analcohol (methanol in particular) or water are preferred. In a solventcontaining at least hydrocarbon, the ratio of an alcohol (methanol inparticular) to other solvents (for example, an ester such as ethylacetate or an ether such as tetrahydrofuran) is, for example,former/latter (in volume ratio at 25° C.)=10/90 to 99/1, preferablyformer/latter (in volume ratio at 25° C.)=30/70 to 98/2, and morepreferably former/latter (in volume ratio at 25° C.)=50/50 to 97/3.

The use amount of the precipitation or reprecipitation solvent isappropriately chosen in consideration of efficiency, yield and otherfactors. Generally, to 100 parts by mass of a polymer solution, 100 to10000 parts by mass, preferably 200 to 2000 parts by mass and morepreferably 300 to 1000 parts by mass are used.

The nozzle diameter used for feeding a polymer solution into aprecipitation or reprecipitation solvent (poor solvent) is preferably 4mm φ or less (for example, 0.2 to 4 mm φ). The feeding velocity(dropping speed) of a polymer solution to a poor solvent is, forexample, 0.1 to 10 m/sec and preferably roughly 0.3 to 5 m/sec in termsof linear velocity.

Precipitation or reprecipitation is preferably carried out underagitation. As the stirring wing used for such agitation, a disc turbine,a fan turbine (including a paddle), a curved blade turbine, anarrow-feather blade turbine, a Phaudler-type one, an angled blade fanturbine, a propeller, a multistage-type one, an anchor-type (orhorseshoe type) one, a gate-type one, a double ribbon and a screw can beused. Agitation is preferably continued, even after the completion ofpolymer solution feeding, for 10 min or more, particularly for 20 min ormore. In case where the agitation period is short, there occur somecases where the monomer content in polymer particles cannot besufficiently reduced. In addition, a polymer solution can be mixed andagitated with a poor solvent by using a line mixer instead of a stirringwing.

The temperature for precipitation or reprecipitation is chosenappropriately in consideration of efficiency and operability, usuallybeing around 0 to 50° C. and preferably around room temperature (forexample, about 20 to 35° C.). Precipitation or reprecipitation operationcan be conducted using a conventional mixing vessel such as a agitationtank by any of the well-known methods including a batch process orcontinuous process.

The particulate polymer obtained by precipitation or reprecipitation isusually subjected to a conventional solid-liquid separation operationsuch as filtration or centrifugal separation, and dried for practicaluse. Filtration uses a solvent-resistant filter material and isconducted under an ordinary or reduced pressure (preferably under areduced pressure) at a temperature of around 30 to 100° C., preferablyaround 30 to 50° C.

Meanwhile, the resin, which has been once precipitated and separated,may thereafter be dissolved in a solvent again, and be brought intocontact with a solvent in which the resin is sparingly soluble orinsoluble.

Namely, one may employ the following processes: after the completion ofthe aforementioned radical polymerization reaction, the resin isdeposited by bringing the reaction mixture into contact with a solventin which the polymer is sparingly soluble or insoluble (process a), andis separated from the solution (process b), and then a resin solution Ais newly prepared by dissolving the resin in a solvent (process c).Thereafter, the resin solid is deposited by bringing a solvent in whichthe resin is sparingly soluble or insoluble in a volume amount notexceeding 10 times (preferably 5 times) of that of the resin solution Ainto contact with the resin solution A (process d), and the depositedresin is separated (process e).

The used for the preparation of the resin solution A may be the one usedfor dissolving monomers in the polymerization reaction, or may be thesame as or different from the solvent used in the polymerizationreaction.

(D) Dissolution Inhibitive Compound Having Molecular Weight of 3,000 orLower and Decomposing by Action of Acid to Show Enhanced Solubility inAlkaline Developing Solution (hereinafter referred to also as“dissolution inhibitive compound”)

The positive resist composition of the invention may contain adissolution inhibitive compound which has a molecular weight of 3,000 orlower and decomposes by the action of an acid to show enhancedsolubility in an alkaline developing solution (hereinafter referred toalso as “dissolution inhibitive compound”).

The dissolution inhibitive compound preferably is an alicycilc oraliphatic compound having an acid-decomposable group, such as the cholicacid derivatives containing an acid-decomposable group which aredescribed in Proceeding of SPIE, 2724, 355(1996), so as not to reducetransmission at wavelengths of 220 nm and shorter. Examples of theacid-decomposable group and alicyclic structure are the same as thosedescribed above with regard to the resin as component (A).

The dissolution inhibitive compound in the invention has a molecularweight of 3,000 or lower, preferably 300-3,000, more preferably500-2,500.

The amount of the dissolution inhibitive compound to be added ispreferably 1-30% by mass, more preferably 2-20% by mass, based on allsolid components of the positive resist composition.

Examples of the dissolution inhibitive compound are shown below, but thecompound should not be construed as being limited to the followingexamples.

(E) Basic Compound

The positive resist composition of the invention preferably contains abasic compound (E) so as to be reduced in performance changes with thelapse of time from exposure to heating.

Preferred examples of the basic compound include compounds havingstructures represented by the following formulae (A) to (E).

In general formulae (A) to (E),

R²⁰⁰, R²⁰¹, and R²⁰² may be the same or different and each represent ahydrogen atom, alkyl group having 1-20 carbon atoms, cycloalkyl grouphaving 3-20 carbon atoms, or aryl group having 6-20 carbon atoms,provided that R²⁰¹ and R²⁰² may be bonded to each other to form a ring.

The alkyl group may be unsubstituted or may have one or moresubstituents. The alkyl group having one or more substituents preferablyis an aminoalkyl group having 1-20 carbon atoms, hydroxyalkyl grouphaving 1-20 carbon atoms, or cyanoalkyl group having 1-20 carbon atoms.

R²⁰³, R²⁰⁴, R²⁰⁵, and R²⁰⁶ may be the same or different and eachrepresent an alkyl group having 1-20 carbon atoms.

The alkyl groups in general formulae (A) to (E) preferably areunsubstituted.

Examples of the basic compound include primary, secondary, or tertiaryaliphatic amines, aromatic amines, heterocyclic amines, amidederivatives, imide derivatives, and nitrogen-containing compounds havinga cyano group, these compounds being substituted or unsubstituted.Preferred of these are aliphatic amines, aromatic amines, andheterocyclic amines. Preferred examples of substituents which may bepossessed are amino, alkyl, alkoxy, acyl, acyloxy, aryl, aryloxy, nitro,cyano, ester, and lactone groups.

Those basic compounds may be used alone or in combination of two or morethereof.

The amount of the basic compound to be used is generally 0.001-10% bymass, preferably 0.01-5% by mass, based on the solid components of thepositive resist composition.

The proportion of the acid generator to the basic compound in thecomposition is preferably such that the acid generator/basic compoundratio (by mole) is from 2.5 to 300. Namely, that molar ratio ispreferably 2.5 or higher from the standpoints of sensitivity andresolution and is preferably 300 or lower from the standpoint ofinhibiting resolution from being reduced by the thickening of resistpattern lines with the lapse of time from exposure to heat treatment.The acid generator/basic compound ratio (by mole) is more preferablyfrom 5.0 to 200, even more preferably from 7.0 to 150.

(E) Surfactant

The positive resist composition of the invention preferably furthercontains one or more surfactants (E). It is preferred that thecomposition should contain any one of or two or more of fluorochemicaland/or silicone surfactants (fluorochemical surfactants, siliconesurfactants, and surfactants containing both fluorine atoms and siliconatoms).

When the positive resist composition of the invention contains such asurfactant (E), it can show satisfactory sensitivity and resolution whenirradiated with an exposure light having a wavelength of 250 nm orshorter, especially 220 nm or shorter, and give a resist pattern havingsatisfactory adhesion and reduced in development defects.

Examples of the fluorochemical and/or silicone surfactants include thesurfactants described in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745,JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834,JP-A-9-54432, JP-A-9-5988, JP-A-2002-277862, and U.S. Pat. Nos.5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143,5,294,511, and 5,824,451. It is also possible to use the followingcommercial surfactants as they are.

Examples of usable commercial surfactants include fluorochemical orsilicone surfactants such as F-Top EF301 and FE303 (manufactured by NewAkita Chemical Company), Fluorad FC430, 431, and 4430 (manufactured bySumitomo 3M Ltd.), Megafac F171, F173, F176, F189, F113, F110, F177,F120, and R08 (manufactured by Dainippon Ink & Chemicals, Inc.), SurflonS-382 and SC101, 102, 103, 104, 105, and 106 (manufactured by AsahiGlass Co., Ltd.), Troysol S-366 (manufactured by Troy Chemical Co.,Ltd.), GF-300 and GF-150 (manufactured by Toagosei Co., Ltd.), SurflonS-393 (manufactured by Seimi Chemical Co., Ltd.), F-Top EF121, EF122A,EF122B, RF122C, EF125M, EF135M, EF351, 352, EF801, EF802, and EF601(manufactured by JEMCO Inc.), PF636, PF656, PF6320, and PF6520(manufactured by OMNOVA Inc.), and FTX-204D, 208G, 218G, 230G, 204D,208D, 212D, 218, and 222D (manufactured by NEOS Co., Ltd.). Polysiloxanepolymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) can alsobe used as a silicone surfactant.

Also usable besides the known surfactants shown above is a surfactantcomprising a polymer having a fluoroaliphatic group derived from afluoroaliphatic compound and produced by the telomerization method (alsocalled telomer method) or oligomerization method (also called oligomermethod). The fluoroaliphatic compound can be synthesized by the methoddescribed in JP-A-2002-90991.

The polymer having a fluoroaliphatic group preferably is a copolymer ofa monomer having a fluoroaliphatic group with a poly(oxyalkylene)acrylate and/or a poly(oxyalkylene) methacrylate. This copolymer may beone in which the monomer units are randomly distributed or be a blockcopolymer. Examples of the poly(oxyalkylene) group includepoly(oxyethylene), poly(oxypropylene), and poly(oxybutylene). Thepoly(oxyalkylene) group may be a unit having, in the same chain,alkylenes having different chain lengths, such as a poly(blocks ofoxyethylene, oxypropylene, and oxyethylene) or poly(blocks ofoxyethylene and oxypropylene) group. The copolymer of a monomer having afluoroaliphatic group with a poly(oxyalkylene) acrylate (ormethacrylate) is not limited to binary copolymers, and may be acopolymer of three or more monomers which is obtained bycopolymerization in which two or more different monomers each having afluoroaliphatic group, two or more different poly(oxyalkylene) acrylates(or methacrylates), etc. are simultaneously copolymerized.

Examples of commercial surfactants include Megafac F178, F-470, F-473,F-475, F-476, and F-472 (manufactured by Dainippon Ink & Chemicals,Inc.). Examples of the polymer having a fluoroaliphatic group furtherinclude a copolymer of an acrylate (or methacrylate) having a C₆F₁₃group with a poly(oxyalkylene) acrylate (or methacrylate) and acopolymer of an acrylate (or methacrylate) having a C₃F₇ group withpoly(oxyethylene) acrylate (or methacrylate) and poly(oxypropylene)acrylate (or methacrylate).

Surfactants other than the fluorochemical and/or silicone surfactantsmay be used in the invention. Examples thereof include nonionicsurfactants including polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether,polyoxyethylene/polyoxypropylene block copolymers, sorbitan/fatty acidesters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate, and sorbitantristearate, and polyoxyethylene-sorbitan/fatty acid esters such aspolyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, and polyoxyethylene sorbitan tristearate.

Those surfactants may be used alone or in combination of two or morethereof.

The amount of the surfactant (E) to be used is preferably 0.01-10% bymass, more preferably 0.1-5% by mass, based on the total amount of thepositive resist composition (excluding the solvent).

(F) Solvent

Examples of solvents usable in dissolving the components described abovefor preparing the positive resist composition include organic solventssuch as alkylene glycol monoalkyl ether carboxylates, alkylene glycolmonoalkyl ethers, alkyl lactates, alkyl alkoxypropionates, cycliclactones having 4-10 carbon atoms, monoketone compounds having 4-10carbon atoms and optionally having a ring, alkylene carbonates,alkoxyalkyl acetates, and alkyl pyruvates.

Preferred examples of the alkylene glycol monoalkyl ether carboxylatesinclude propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, propylene glycol monoprpopyl ether acetate,propylene glycol monobutyl ether acetate, propylene glycol monomethylether propionate, propylene glycol monoethyl ether propionate, ethyleneglycol monomethyl ether acetate, and ethylene glycol monoethyl etheracetate.

Preferred examples of the alkylene glycol monoalkyl ethers includepropylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monopropyl ether, propylene glycol monobutyl ether,ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether.

Preferred examples of the alkyl lactates include methyl lactate, ethyllactate, propyl lactate, and butyl lactate.

Preferred examples of the alkyl alkoxypropionates include ethyl3-ethoxypropionate, methyl 3-methoxypropionate, methyl3-ethoxypropionate, and ethyl 3-methoxypropionate.

Preferred examples of the cyclic lactones having 4-10 carbon atomsinclude β-propiolactone, β-butyrolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-octanolactone, and α-hydroxy-γ-butyrolactone.

Preferred examples of the monoketone compounds having 4-10 carbon atomsand optionally having a ring include 2-butanone, 3-methylbutanone,pinacolone, 2-pentanone, 3-pentanone, 3-methyl-2-pentanone,4-methyl-2-pentanone, 2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone,3-decanone, 4-decanone, 5-hexen-2-one, 3-penten-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methylcycloheptanone, and 3-methylcycloheptanone.

Preferred examples of the alkylene carbonates include propylenecarbonate, vinylene carbonate, ethylene carbonate, and butylenecarbonate.

Preferred examples of the alkoxyalkyl acetates include 2-methoxyethylacetate, 2-ethoxyethyl acetate, 2-(2-ethoxyethoxy)ethyl acetate,3-methoxy-3-methylbutyl acetate, and 1-methoxy-2-propyl acetate.

Preferred examples of the alkyl pyruvates include methyl pyruvate, ethylpyruvate, and propyl pyruvate.

Preferred solvents include solvents having a boiling point of 130° C. orhigher at ordinary temperature and ordinary pressure. Specific examplesthereof include cyclopentanone, γ-butyrolactone, cyclohexanone, ethyllactate, ethylene glycol monoethyl ether acetate, propylene glycolmonomethyl ether acetate, ethyl 3-ethoxypropionate, ethyl pyruvate,2-ethoxyethyl acetate, 2-(2-ethoxyethoxy)ethyl acetate, and propylenecarbonate.

In the invention, those solvents may be used alone or in combination oftwo or more thereof.

In the invention, a mixed solvent prepared by mixing at least onesolvent containing one or more hydroxyl groups in the structure with atleast one solvent containing no hydroxyl group may be used as theorganic solvent.

Examples of the solvent containing one or more hydroxyl groups includeethylene glycol, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, propylene glycol, propylene glycol monomethyl ether,propylene glycol monoethyl ether, and ethyl lactate. Preferred of theseare propylene glycol monomethyl ether and ethyl lactate.

Examples of the solvent containing no hydroxyl group include propyleneglycol monomethyl ether acetate, ethyl ethoxypropionate, 2-heptanone,γ-butyrolactone, cyclohexanone, butyl acetate, N-methylpyrrolidone,N,N-dimethylacetamide, and dimethyl sulfoxide. Especially preferred ofthese are propylene glycol monomethyl ether acetate, ethylethoxypropionate, 2-heptanone, γ-butyrolactone, cyclohexanone, and butylacetate. Most preferred are propylene glycol monomethyl ether acetate,ethyl ethoxypropionate, and 2-heptanone.

The proportion (by mass) of the solvent containing one or more hydroxylgroups to the solvent containing no hydroxyl group may be from 1/99 to99/1, and is preferably from 10/90 to 90/10, more preferably from 20/80to 60/40. A mixed solvent in which the content of the solvent containingno hydroxyl group is 50% by weight or higher is especially preferredfrom the standpoint of evenness of application.

(G) Alkali-Soluble Resin

The positive resist composition of the invention can further contain aresin (G) which is insoluble in water and soluble in an alkalinedeveloping solution and contains no acid-decomposable group.Incorporation of this resin improves sensitivity.

A novolak resin having a molecular weight of about 1,000-20,000 or apolyhydroxystyrene derivative having a molecular weight of about3,000-50,000 can be used as the alkali-soluble resin in the invention.However, Since these polymers considerably absorb light having awavelength of 250 nm or shorter, it is preferred to use the polymers ina partly hydrogenated form or in an amount up to 30% by weight based onall resins.

A resin having carboxyl groups as alkali-soluble groups can also beused. The resin having carboxyl groups preferably has a mono- orpolycyclic aliphatic hydrocarbon group so as to improve dry etchingresistance. Examples thereof include copolymers of (meth)acrylic acidand a methacrylic ester having an alicyclic hydrocarbon structure whichis not acid-decomposable and resins of a (meth)acrylic ester having analicyclic hydrocarbon group having a carboxyl group at the end.

(H) Carboxylic Acid Onium Salt

The positive resist composition of the invention may contain acarboxylic acid onium salt (H). Examples of the carboxylic acid oniumsalt include carboxylic acid sulfonium salts, carboxylic acid iodoniumsalts, and carboxylic acid ammonium salts. Especially preferredcarboxylic acid onium salts (H) of these are iodonium salts andsulfonium salts. The carboxylic acid onium salt (H) to be used in theinvention preferably is one in which the carboxylate residue containsneither an aromatic group nor a carbon-carbon double bond. An especiallypreferred anion part is an alkanecarboxylic acid anion in which thealkyl group is a linear, branched, monocyclic, or polycyclic alkylhaving 1-30 carbon atoms. More preferred is such carboxylic acid anionin which the alkyl group has been partly or wholly substituted byfluorine. The alkyl chain may contain an oxygen atom therein.Incorporation of the carboxylic acid onium salt not only improvessensitivity and resolution while securing transparency to light having awavelength of 220 nm or shorter but also attains improvements inresolution independence from the degree of line density and in exposuremargin.

Examples of the fluorine-substituted carboxylic acid anion include theanions of fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid,pentafluoropropionic acid, heptafluorobutyric acid, nonafluoropentanoicacid, perfluorododecanoic acid, perfluorotridecanoic acid,perfluorocyclohexanecarboxylic acid, and 2,2-bistrifluoromethylpropionicacid.

Those carboxylic acid onium salts (H) can be synthesized by reacting asulfonium hydroxide, iodonium hydroxide, or ammonium hydroxide withcarboxylic acids in an appropriate solvent with the acid of silveroxide.

The content of the carboxylic acid onium salt (H) in the composition isdesirably 0.1-20% by mass, preferably 0.5-10% by mass, more preferably1-7% by mass, based on all solid components of the composition.

Other Additives

A dye, plasticizer, photosensitizer, light absorber, compound enhancingsolubility in developing solutions (e.g., a phenolic compound having amolecular weight of 1,000 or lower or an alicyclic or aliphatic compoundhaving one or more carboxyl groups), and other additives may be furtherincorporated according to need into the positive resist composition ofthe invention.

The phenolic compound having a molecular weight of 1,000 or lower can beeasily synthesized by persons skilled in the art while referring tomethods described in, e.g., JP-A-4-122938, JP-A-2-28531, U.S. Pat. No.4,916,210, and European Patent 219,294.

Examples of the alicyclic or aliphatic compound having one or morecarboxyl groups include carboxylic acid derivatives having a steroidstructure, such as cholic acid, deoxycholic acid, and lithocholic acid,adamantanecarboxylic acid derivatives, adamantanedicarboxylic acid,cyclohexanecarboxylic acid, and cyclohexanedicarboxylic acid. However,the alicyclic or aliphatic compound should not be construed as beinglimited to these.

[Properties of Resist Composition]

It is preferred that the positive resist composition of the invention beused in a film thickness of 30-250 nm from the standpoint of improvingresolution. More preferably, the composition is used in a film thicknessof 30-200 nm. Such a film thickness can be attained by imparting anappropriate viscosity to the positive resist composition by regulatingthe solid concentration in the composition so as to be in an adequaterange and by improving applicability and film-forming properties.

The total solid concentration in the positive resist composition isgenerally 1-10% by mass, preferably 1-8% by mass, more preferably1.0-7.0% by mass.

[Method of Pattern Formation]

When the positive resist composition of the invention is used, thecomponents described above are dissolved in a given organic solvent,preferably the mixed solvent, and the resultant solution is filtered andthen applied to a given substrate in the following manner. The filter tobe used for the filtration preferably is one which is made ofpolytetrafluoroethylene, polyethylene, or nylon and has a pore size of0.1 μm or smaller, more preferably 0.05 μm or smaller, even morepreferably 0.03 μm or smaller.

For example, the positive resist composition is applied to a base suchas one for use in producing precision integrated-circuit elements (e.g.,a silicon base coated with silicon dioxide) by an appropriate coatingtechnique using a spinner, coater, or the like. The coating film isdried to form a photosensitive film.

This photosensitive film is irradiated with actinic rays or a radiationthrough a given mask and then preferably baked (heated). This film isdeveloped and rinsed. Thus, a satisfactory pattern can be obtained.

Examples of the actinic rays or radiation include infrared, visiblelight, ultraviolet, far ultraviolet, X rays, and electron beams.Preferred are far ultraviolet rays having a wavelength of preferably 250nm or shorter, more preferably 220 nm or shorter, such as, e.g., KrFexcimer laser light (248 nm), ArF excimer laser light (193 nm), and F₂excimer laser light (157 nm), X rays, electron beams, and the like. Morepreferred are lights having a wavelength of 1-200 nm. Especiallypreferred are ArF excimer laser light, F₂ excimer laser light, EUV (13nm), and electron beams.

In a development step, an alkaline developing solution is used in thefollowing manner. As an alkaline developing solution for the resistcomposition can be used an alkaline aqueous solution of, e.g., aninorganic alkali such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium metasilicate, or ammonia water, aprimary amine such as ethylamine or n-propylamine, a secondary aminesuch as diethylamine or di-n-butylamine, a tertiary amine such astriethylamine or methyldiethylamine, an alcoholamine such asdimethylethanolamine or triethanolamine, a quaternary ammonium salt suchas tetramethylammonium hydroxide or tetraethylammonium hydroxide, or acyclic amine such as pyrrole or piperidine.

It is also possible to add an alcohol or a surfactant in an appropriateamount to the alkaline developing solution to be used.

The alkali concentration of the alkaline developing solution isgenerally 0.1-20% by mass.

The pH of the alkaline developing solution is generally 10.0-15.0.

Pure water is used as a rinse, optionally after an appropriate amount ofa surfactant is added thereto.

After the development or rinsing, a treatment can be conducted in whichthe developing solution or rinse adherent to the pattern is removed witha supercritical fluid.

When the photosensitive resist film is irradiated with actinic rays or aradiation, this exposure may be conducted while filling the spacebetween the resist film and a lens with a liquid (immersion medium)having a higher refractive index than air (immersion exposure). Thisexposure technique can heighten resolution. The immersion medium to beused can be any liquid having a higher refractive index than air.However, pure water is preferred. An overcoat layer may be furtherformed on the photosensitive film in order to prevent the photosensitivefilm from coming into direct contact with the immersion medium inimmersion exposure. This overcoat layer inhibits composition extractionfrom the photosensitive film to the immersion medium to thereby diminishdevelopment defects.

The immersion liquid to be used in the immersion exposure will beexplained below.

The immersion liquid preferably is a liquid which is transparent to theexposure light to be used and in which the temperature coefficient ofrefractive index is as small as possible so as to minimize thedeformation of an optical image to be projected on the resist. However,especially when the exposure light source is an ArF excimer laser(wavelength: 193 nm), it is preferred to use water from the standpointsof availability and handleability besides the standpoints shown above.

Furthermore, a medium having a refractive index of 1.5 or higher can beused from the standpoint of being capable of further improvingrefractive index. This medium may be an aqueous solution or an organicsolvent.

In the case where water is used as the immersion liquid, an additive(liquid) in which the resist layer on the wafer does not dissolve andthe influence of which on the optical coat on the lower side of the lenselement is negligible may be added in a slight proportion in order toreduce the surface tension of the water and enhance surface activity.This additive preferably is an aliphatic alcohol almost equal to waterin refractive index. Examples thereof include methyl alcohol, ethylalcohol, and isopropyl alcohol. The addition of an alcohol almost equalto water in refractive index brings about an advantage that even whenthe alcohol component contained in the water vaporizes to cause a changein alcohol concentration, the change in refractive index of the liquidas a whole can be kept exceedingly slight. On the other hand, in casewhere a substance which is not transparent to 193-nm light or animpurity considerably differing from water in refractive index has comeinto the water, this leads to the deformation of an optical image to beprojected on the resist. It is therefore preferred that the water to beused should be distilled water. Pure water which has undergonefiltration through an ion-exchange filter or the like may be used.

The electrical resistance of the water desirably is 18.3 MΩ·cm orhigher, and the TOC (organic concentration) therein is desirably 20 ppbor lower. Furthermore, it is desirable that the water should have beendegassed.

By heightening the refractive index of the immersion liquid,lithographic performance can be enhanced. From this standpoint, anadditive serving to heighten the refractive index may be added to thewater, or heavy water (D₂O) may be used in place of the water.

A film sparingly soluble in the immersion liquid (hereinafter the filmis referred to also as “top coat”) may be formed between the immersionliquid and the resist film formed from the positive resist compositionof the invention in order to prevent the resist film from coming intodirect contact with the immersion liquid. The functions required of thetop coat include applicability to the resist surface, transparency toradiations, in particular, one having a wavelength of 193 nm, and poorsolubility in the immersion liquid. The top coat preferably is one whichdoes not intermix with the resist and is evenly applicable to the resistsurface.

From the standpoint of transparency at 193 nm, the top coat preferablyis a polymer containing no aromatic. Examples thereof includehydrocarbon polymers, acrylic ester polymers, poly(methacrylic acid),poly(acrylic acid), poly(vinyl ether)s, silicon-containing polymers, andfluorine-containing polymers. Because extraction of impurities from thetop coat into the immersion liquid results in the fouling of the opticallens, the top coat preferably is one in which the amount of residualmonomer components contained in the polymer constituting the top coat issmaller.

For removing the top coat, a developing solution may be used.Alternatively, the top coat may be removed by separately using aremover. The remover preferably is a solvent which is less apt toinfiltrate into the resist. It is preferred that the top coat be removedwith an alkaline developing solution because a removal step can beconducted simultaneously with a development step. The top coatpreferably is acidic from the standpoint of removal with an alkalinedeveloping solution. However, the top coat may be either neutral oralkaline from the standpoint of the property of not intermixing with theresist.

The smaller the difference in refractive index between the top coat andthe immersion liquid, the more the resolution improves. In the casewhere an ArF excimer laser (wavelength: 193 nm) is used in combinationwith water as an immersion liquid, the top coat for ArF immersionexposure preferably has a refractive index close to that of theimmersion liquid. From the standpoint of attaining a refractive indexcloser to that of the immersion liquid, the top coat preferably containsfluorine atoms therein. From the standpoints of transparency andrefractive index, the top coat preferably is thin.

It is preferred that the top coat intermixes with neither the resist northe immersion liquid. From this standpoint, when the immersion liquid iswater, the solvent for the top coat preferably is a medium which ispoorly soluble in the resist solvent and is water-insoluble. In the casewhere the immersion liquid is an organic solvent, the top coat may beeither water-soluble or water-insoluble.

The resist composition of the invention preferably gives a resist filmwith which water has a receding contact angle of 65° or larger. Thevalue of receding contact angle is one measured at ordinary temperatureand ordinary pressure at the time when the droplet begins to fall as aresult of resist film inclination. In general, receding contact anglenearly correlates with sliding angle. Namely, the larger the recedingcontact angle and the smaller the sliding angle, the better the waterrepellency.

EXAMPLES

The invention will be explained below in more detail by reference toExamples, but the contents of the invention should not be construed asbeing limited by the following Examples.

Examples 1 to 44 and Comparative Examples 1 and 2 Synthesis Example(Synthesis of Resin (1))

Under nitrogen gas feeding, 8.6 g of cyclohexanone was charged in athree-necked flask, which was heated to 80° C. Into the flask, 9.8 g of2-adamantylisopropyl methacrylate, 4.4 g of dihydroxyadamantylmethacrylate, 8.9 g of norbornanelactone methacrylate, and a solutionobtained by dissolving a polymerization initiator V601 (manufactured byWako Pure Chemical Industries, Ltd.) in 79 g of cyclohexanone in anamount of 8% by mole relative to the moles of the monomers were addeddropwise over a period of 6 hr. After the completion of dropwiseaddition, the reaction was continued for 2 hr at 80° C. After cooling,the reaction solution was introduced in a mixture of 800 ml hexane and200 ml ethyl acetate in 20 min. The deposited powder was filtered anddried to give Resin (1) in 19 g. The weight average molecular weight ofthe resin thus obtained was 9800 as determined through calculation forstandard polystyrene, and the degree of dispersion (Mw/Mn) thereof was1.9.

Resins (2) to (30) were synthesized in similar manners to that for Resin(1).

Resin (31) was synthesized in the same manner as in Example 1 ofJapanese Patent Laid-open No. 2005-156726.

The structures, compositions, molecular weights, etc. of theacid-decomposable resins (A) used in the Examples are shown below. Withrespect to each composition, the resin structural formula No. and theproportions (proportions of the units, in the left-to-right order, inthe structural formula) are shown.

TABLE 1 Resin Composition Mw Mw/Mn 1 39/20/41 9800 1.9 2 40/22/38 120002.0 3 34/33/33 11000 2.3 4 45/15/40 10500 2.1 5 35/15/50 6700 2.2 630/25/45 8400 2.3 7 39/20/41 10500 2.1 8 49/10/41 9500 2.5 9 35/32/3314000 2.6 10 35/35/30 6700 2.3 11 40/22/38 8500 2.5 12 40/20/35/5 125002.4 13 50/50 14000 1.9 14 40/15/40/5 10000 1.8 15 50/50 8300 1.5 1640/15/40/5 9800 2.3 17 50/50 5200 2.1 18 35/20/40/5 6100 2.3 19 30/30/30/10 8600 2.5 20 40/20/35/5 12000 2.1 21 30/20/50 8500 2.0 22 30/20/40/10 8000 2.0 23 40/10/50 6000 1.8 24  30/20/40/10 7000 2.1 2550/20/30 6000 1.8 26 35/30/35 9800 1.8 27 25/25/50 6700 2.0 28 50/25/2512000 2.0 29 50/30/20 10000 2.0 30  40/20/20/10 6400 2.1 31 40/10/507700 2.0

Synthesis Example (1) Synthesis of Resins (C-1) and (C-2)

A mixture of 0.06 mol of3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl2-trifluoromethylmethacrylate and 0.04 mol of(5-norbomene-2-methyl)-1,1,1,3,3,3-hexafluoropropan-2-ol was prepared.While this mixture was being stirred at 80° C. in a nitrogen atmosphere,1.5 mol % polymerization initiator V-59, manufactured by Wako PureChemical Industries, Ltd., was added thereto. This mixture was stirredunder those conditions for 3 hours. Thereafter, the mixture was furtherstirred for 12 hours while adding 1.5 mol % polymerization initiatorV-59 at an interval of 3 hours. After completion of the reaction, thisliquid reaction mixture (C-1) was dissolved in 20 mL of THF and theresultant solution was cooled to room temperature. This solution waspoured into 800 mL of hexane to cause crystallization. The white powderprecipitated was taken out by filtration. Thus, the target resin (C-1)was recovered.

The composition of the polymer was determined by ¹H NMR and was found tobe 60/40 (proportions of the units, in the left-to-right order, in thestructural formula). The weight-average molecular weight and dispersityratio thereof, as determined through measurement by GPC and calculationfor standard polystyrene, were 8,800 and 1.5, respectively.

Resin (C-2) was synthesized in the same manner as described above,except that the monomers were changed and the feed proportions werechanged to 70/30 (proportions for the units, in the left-to-right order,in the structural formula). The polymer composition of resin (C-2) wasdetermined by ¹H NMR and was found to be 68/32. The weight-averagemolecular weight and dispersity ratio thereof, as determined throughmeasurement by GPC and calculation for standard polystyrene, were 11,000and 1.7, respectively.

Synthesis Example (2) Synthesis of Resin (C-3)

In 44 mL of chlorobenzene were dissolved 0.262 g ofdi-μ-chlorobis[(η-allyl)palladium(II)] and 0.488 g of silverhexafluoroantimonate. This solution was stirred at room temperature.After 20 minutes; the reaction mixture was filtered. The filtrate wasadded to a liquid mixture composed of 20 g of5-norbornene-1,1,1,3,3,3-hexafluoropropan-2-ol, 0.2 mL of water, and 170mL of chlorobenzene. The resultant mixture was stirred at roomtemperature for 20 hours and then added to 1,200 mL of methanol. Theresin precipitated was taken out by filtration. Subsequently, the resinwas dissolved in 150 mL of chlorobenzene. Thereto were added 30 mL ofmethanol and 3.2 g of sodium borohydride. This mixture was stirred atroom temperature for 3 hours and then allowed to stand at roomtemperature for 24 hours. The particles of Pd(0) precipitated wereremoved by filtration, and the filtrate was poured into 800 mL ofmethanol. The resin precipitated was taken out by filtration to obtainthe target resin (C-3).

The weight-average molecular weight and dispersity ratio of the resin,as determined through measurement by GPC and calculation for standardpolystyrene, were 8,000 and 1.4, respectively.

Synthesis Example (3) Synthesis of Resins (C-4) to (C-6)

In 70 mL of propylene glycol monomethyl ether acetate was dissolved 20 gof1,1,1,3,3,3-hexafluoro-2-(4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl)propan-2-ylmethacrylate. To this solution was added 3 mol % polymerizationinitiator V-601, manufactured by Wako Pure Chemical Industries, Ltd. Ina nitrogen atmosphere, the resultant mixture was added dropwise over 6hours to 10 mL of a propylene glycol monomethyl ether acetate solutionheated at 80° C. After completion of the dropwise addition, the reactionmixture was stirred for 2 hours to obtain a liquid reaction mixture(C-4). After completion of the reaction, the liquid reaction mixture(C-4) was cooled to room temperature and poured into a 4.5-fold amountof hexane to cause crystallization. The white powder precipitated wastaken out by filtration. Thus, the target resin (C-4) was recovered.

The weight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 8,500 and 1.4, respectively.

Resin (C-5) was synthesized in the same manner as in Synthesis Example(3) in which the monomers were fed in proportions of 80/20 (proportionsfor the units, in the left-to-right order, in the structural formula).For the crystallization, methanol was used as a solvent. The compositionof the polymer was determined by ¹H NMR and was found to be 80/20. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 13,000 and 2.1, respectively.

Resin (C-6) was synthesized in the same manner as in Synthesis Example(3) in which the monomers were fed in proportions of 70/30 (proportionsfor the units, in the left-to-right order, in the structural formula).For the crystallization, methanol was used as a solvent. The compositionof the polymer was determined by ¹H NMR and was found to be 70/30. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 18,000 and 2.3, respectively.

Resin (C-7) was synthesized in the same manner as in Synthesis Example(1) in which the monomers were fed in proportions of 50/50 (proportionsfor the units, in the left-to-right order, in the structural formula).For the crystallization, methanol was used as a solvent. The compositionof the polymer was determined by ¹H NMR and was found to be 50/50. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 5,200 and 1.9, respectively.

Resin (C-8) was synthesized in the same manner as in Synthesis Example(3) in which the monomers were fed in proportions of 50/50 (proportionsfor the units, in the left-to-right order, in the structural formula).For the crystallization, methanol was used as a solvent. The compositionof the polymer was determined by ¹H NMR and was found to be 50/50. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 10,200 and 2.2, respectively.

Resin (C-9) was synthesized in the same manner as in Synthesis Example(3) in which the monomers were fed in proportions of 60/40 (proportionsfor the units, in the left-to-right order, in the structural formula).For the crystallization, hexane was used as a solvent. The compositionof the polymer was determined by ¹H NMR and was found to be 60/40. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 7,200 and 2.2, respectively.

Resin (C-10) was synthesized in the same manner as in Synthesis Example(1) in which the monomers were fed in proportions of 30/30/40(proportions for the units, in the left-to-right order, in thestructural formula). For the crystallization, methanol was used as asolvent. The composition of the polymer was determined by ¹H NMR and wasfound to be 32/32/36. The weight-average molecular weight and dispersityratio thereof, as determined through measurement by GPC and calculationfor standard polystyrene, were 5,600 and 2.0, respectively.

Synthesis Example (4) Synthesis of Resin (C-11)

In propyleneglycol monomethyl ether acetate, 50 g of(3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl)methacrylate was dissolved to give a 200 mL solution. This mixture wassubjected to agitation at 80° C. under nitrogen atmosphere. To thismixture under this condition was added 5 molar % of V-601, apolymerization initiator manufactured by Wako Pure Chemical Industries,Ltd.

And the resulting mixture was agitated for 5 hr as it was. Aftercompletion of the reaction, the mixture was cooled to room temperature,subjected to precipitation into 5 times volume hexane. The separatedwhite powder was collected by filtration to obtain the target resin(C-11).

The weight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 9300 and 1.4, respectively.

Resin (C-12) was synthesized in the same manner as in Synthesis Example(3) except that the charging compositional ratio was set at 50/50 andthat the amount of the polymerization initiator was changed to 5 molar%. The polymer compositional ratio determined by ¹H NMR was found to be50/50. The weight-average molecular weight and dispersity ratio thereof,as determined through measurement by GPC and calculation for standardpolystyrene, were 8800 and 1.8, respectively.

Resin (C-13) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratios were setat 40/30/30. The polymer compositional ratios determined by ¹H NMR werefound to be 39/30/31. The weight-average molecular weight and dispersityratio thereof, as determined through measurement by GPC and calculationfor standard polystyrene, were 6500 and 1.8, respectively.

Resin (C-14) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratio was set at80/20. The polymer compositional ratio determined by ¹H NMR was found tobe 78/22. The weight-average molecular weight and dispersity ratiothereof, as determined through measurement by GPC and calculation forstandard polystyrene, were 8700 and 1.8, respectively.

Resin (C-15) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratio was set at80/20. The polymer compositional ratio determined by ¹H NMR was found tobe 80/20. The weight-average molecular weight and dispersity ratiothereof, as determined through measurement by GPC and calculation forstandard polystyrene, were 8800 and 1.8, respectively.

Resin (C-16) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratio was set at40/60. For precipitation, methanol was used as the solvent. The polymercompositional ratio determined by ¹H NMR was found to be 40/60. Theweight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 11000 and 1.9, respectively.

Resin (C-17) was synthesized in the same manner as the synthetic methodfor Resin (C-16) except that the charging compositional ratio was set at30/70. The polymer compositional ratio determined by ¹H NMR was found tobe 28/72. The weight-average molecular weight and dispersity ratiothereof, as determined through measurement by GPC and calculation forstandard polystyrene, were 10500 and 1.9, respectively.

Resin (C-18) was synthesized in the same manner as the synthetic methodfor Resin (C-13). The polymer compositional ratio determined by ¹H NMRwas found to be 42/20/38. The weight-average molecular weight anddispersity ratio thereof, as determined through measurement by GPC andcalculation for standard polystyrene, were 7500 and 2.2, respectively.

Resin (C-19) was synthesized in the same manner as the synthetic methodfor Resin (C-16) except that the charging compositional ratios were setat 40/30/30. The polymer compositional ratios determined by ¹H NMR werefound to be 40/33/27. The weight-average molecular weight and dispersityratio thereof, as determined through measurement by GPC and calculationfor standard polystyrene, were 7500 and 2.2, respectively.

Resin (C-20) was synthesized in the same manner as the synthetic methodfor Resin (C-19). The polymer compositional ratio determined by ¹H NMRwas found to be 40/30/30. The weight-average molecular weight anddispersity ratio thereof, as determined through measurement by GPC andcalculation for standard polystyrene, were 8200 and 2.2, respectively.

Resin (C-21) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratio was set at70/30. The polymer compositional ratio determined by ¹H NMR was found tobe 65/35. The weight-average molecular weight and dispersity ratiothereof, as determined through measurement by GPC and calculation forstandard polystyrene, were 5600 and 2.0, respectively.

Resin (C-22) was synthesized in the same manner as in Synthesis Example(3) except that the charging compositional ratio was set at 50/50. Thepolymer compositional ratio determined by ¹H NMR was found to be 50/50.The weight-average molecular weight and dispersity ratio thereof, asdetermined through measurement by GPC and calculation for standardpolystyrene, were 6200 and 2.0, respectively.

Resin (C-23) was synthesized in the same manner as the synthetic methodfor Resin (C-12) except that the charging compositional ratios were setat 30/50/20. The polymer compositional ratio determined by ¹H NMR wasfound to be 29/50/21. The weight-average molecular weight and dispersityratio thereof, as determined through measurement by GPC and calculationfor standard polystyrene, were 8800 and 2.0, respectively.

Resin (C-24) was synthesized in the same manner as in Synthesis Example(3) except that the charging compositional ratios were set at20/40/20/20. The polymer compositional ratios determined by ¹H NMR werefound to be 19/42/20/19. The weight-average molecular weight anddispersity ratio thereof, as determined through measurement by GPC andcalculation for standard polystyrene, were 12000 and 2.2, respectively.

The structures of resins (C-1) to (C-24) are shown below.

<Resist Preparation>

Each set of components shown in Table 2 was dissolved in the solvent toprepare a solution having a solid concentration of 7% by mass. Thissolution was filtered through a 0.1-μm polyethylene filter to prepare apositive resist solution. The positive resist compositions prepared wereevaluated by the following methods. The results obtained are shown inthe following table. In the table, with respect to each componentcomposed of two or more compounds, the proportions of these are shown interms of ratio by mass.

[Image Performance Test]

(Exposure Conditions (1))

Organic antireflection film ARC29A (manufactured by Nissan ChemicalIndustries, Ltd.) was applied to a silicon wafer and baked at 205° C.for 60 seconds to form a 78-nm antireflection film. Each of the positiveresist compositions prepared was applied on the film and baked at 130°C. for 60 seconds to form a 250-nm resist film. The wafer obtained waspattern-wise exposed with an ArF excimer laser scanner (PAS 5500/1100,manufactured by ASML B.V.; NA, 0.75; σ₀/σ₁=0.85/0.55). Thereafter, theresist film was heated at 120° C. for 90 seconds, subsequently developedwith an aqueous solution of tetramethylammonium hydroxide (2.38% bymass) for 30 seconds, rinsed with pure water, and then dried withspinning to obtain a resist pattern.

(Exposure Conditions (2))

Under the conditions (2), a resist pattern is formed by the immersionexposure method using pure water.

Organic antireflection film ARC29A (manufactured by Nissan ChemicalIndustries, Ltd.) was applied to a silicon wafer and baked at 205° C.for 60 seconds to form a 78-nm antireflection film. Each of the positiveresist compositions prepared was applied on the film and baked at 130°C. for 60 seconds to form a 250-nm resist film. The wafer obtained waspattern-wise exposed with an ArF excimer laser immersion scanner (NA,0.75). Pure water was used as an immersion liquid. Thereafter, theresist film was heated at 120° C. for 60 seconds, subsequently developedwith an aqueous solution of tetramethylammonium hydroxide (2.38% bymass) for 30 seconds, rinsed with pure water, and then dried withspinning to obtain resist pattern.

[Profile]

The profile of each of the patterns obtained was examined with ascanning electron microscope (S-4800, manufactured by Hitachi Ltd.) andevaluated.

[Method of Evaluating Pattern Falling]

An exposure amount necessary for reproducing a 130-nm line-and-space 1:1mask pattern was taken as an optimal exposure amount. Each resist filmwas exposed in the optimal exposure amount using line-and-space 1:1patters with dense lines and line-and-space 1:10 patterns with isolatedlines. The line width of the finest mask whose pattern could bereproduced without causing pattern falling was taken as critical linewidth for pattern falling. The smaller the value thereof, the finer thepattern which can be reproduced without causing pattern falling. Namely,smaller values of the critical line width indicate that pattern fallingis less apt to occur.

[Evaluation of Water Following-up Properties]

Each resist composition prepared was applied to an 8-inch silicon waferand baked at 115° C. for 60 seconds to form a 150-nm resist film.Subsequently, 15 mL of distilled water was poured with a pipet onto acentral part of the resist-coated wafer obtained.

A 10 cm-square quartz plate to which a kite string had been attached wasplaced on the resultant puddle of distilled water so as to result in astate in which the space between the wafer and the quartz plate waswholly filled with the distilled water. FIG. 2 diagrammaticallyillustrates a side view of the disposition of the resist-coated wafer,distilled water, and quartz plate which are in that state.

Subsequently, as shown in FIG. 2, the kite string attached to the quartzplate was wound around the rotating part of a motor at a rate of 1cm/sec, with the wafer kept fixed. The motor was on for 0.5 seconds tomove the quartz plate. After the quartz plate movement, the amount ofthe distilled water remaining under the quartz plate was judged based onthe following criteria and used as an index to water following-upproperties.

FIG. 3A to 3D diagrammatically show various patterns observed when thequartz plate was viewed from above after the quartz plate movement. Eachhatched part is a region where the distilled water remained under thequartz plate, while each blank part is a region where the water wasunable to follow up the quartz plate and was replaced by air. Thesamples in which water remained on the whole substrate surface after thequartz plate movement as shown in FIG. 3A are indicated by A; those inwhich air came in an area up to about 10% of the whole substrate area asshown in FIG. 3B are indicated by B; and those in which air came in anarea more than about 10% of the whole substrate area as shown in FIG. 3Care indicated by C.

[Scum Generation]

Organic antireflection film ARC29A (manufactured by Nissan ChemicalIndustries, Ltd.) was applied to a silicon wafer and baked at 205° C.for 60 seconds to form a 78-nm antireflection film. Each positive resistsolution regulated so as to have a solid concentration of 5.5% wasapplied on the film and baked at 115° C. for 60 seconds to form a 160-nmresist film. The wafer obtained was pattern-wise exposed with an ArFexcimer laser scanner (PAS 5500/1100, manufactured by ASML B.V.; NA,0.75; σ₀/σ_(i)=0.85/0.55). Thereafter, the resist film was heated at120° C. for 60 seconds, subsequently developed with an aqueous solutionof tetramethylammonium hydroxide (2.38% by mass) for 30 seconds, rinsedwith pure water, and then dried with spinning to form a pattern.

Scum generation was evaluated based on the amount of a developmentresidue (scum) remaining after the formation of a resist pattern havingline width of 0.15 μm. The samples in which no residue was observed areindicated by A; those in which a residue was observed considerably areindicated by C; and those intermediate between these are indicated by B.

[Measurement of Receding Contact Angle]

Each positive resist composition prepared was applied to a silicon waferand baked at 115° C. for 60 seconds to form a 200-nm resist film. Thereceding contact angle of a water droplet was measured with a dynamiccontact angle meter (manufactured by Kyowa Interface Science Co., Ltd.)by the spreading/contracting method. A droplet having an initial size of7 μL was sucked for 8 seconds at a rate of 6 μL/sec. The dynamic contactangle which became stable during the suction was taken as the recedingcontact angle.

TABLE 2 Composition Evaluation Results Photo- Fluorine- Water acid Basiccontaining Re- follow- gener- com- compound Surfac- Ordinary Immersionceding ing-up Resin ator Solvent pound (C) tant exposure exposurecontact prop- (2 g) (mg) (mass ratio) (mg) (mg) (mg) Profile FallingScum Profile Falling Scum angle erty Ex. 1 1 z2  SL-1/SL-2 N-5 C-1 W-1rectan- 55 A rectan- 60 A 67 A   (80) 60/40 (7) (2) (3) gular gular Ex.2 2 z51 SL-2/SL-4/SL-6 N-6 C-2 W-4 rectan- 60 A rectan- 60 A 65 A (100)40/59/1 (10)  (2) (3) gular gular Ex. 3 3  z2/z62 SL-2/SL-4 N-3 C-1 W-6rectan- 55 A rectan- 55 A 67 A (20/100) 70/30 (6) (2) (3) gular gularEx. 4 4 z55/z65 SL-2/SL-4 — C-1 — T-top 65 A T-top 65 A 67 A (20/100)60/40 (5) Ex. 5 5 z55/z51 SL-3/SL-4 N-6 C-2 W-6 rectan- 60 A rectan- 60A 66 A (20/80) 30/70 (10)  (1) (4) gular gular Ex. 6 6 z44/z65SL-2/SL-4/SL-5 N-1 C-3 W-6 rectan- 55 A rectan- 55 A 70 A (25/80)40/58/2 (7) (5) (4) gular gular Ex. 7 7 z55/z47 SL-1/SL-2 N-4 C-2 W-6rectan- 60 A rectan- 60 A 66 A (30/60) 60/40 (13)  (10) (4) gular gularEx. 8 8 z65 SL-1/SL-2 N-3 C-4 W-2 rectan- 55 A rectan- 55 A 66 A (100)60/40 (6) (3) (3) gular gular Ex. 9 9 z44/z65 SL-2/SL-4/SL-6 N-2 C-3 W-3T-top 55 A T-top 55 A 70 A (50/50) 40/59/1 (9) (3) (3) Ex. 10 10 z51SL-2/SL-4 N-5 C-6 W-5 rectan- 65 A rectan- 65 A 65 A (100) 70/30 (7) (3)(3) gular gular Ex. 11 11 z55/z65 SL-2/SL4 N-1 C-5 W-4 rectan- 70 Arectan- 70 A 65 A (40/60) 60/40 (7) (3) (3) gular gular Ex. 12 12z55/z65 SL-1/SL-2 N-3 C-1 W-1 rectan- 55 A rectan- 60 A 66 A (20/80)50/50 (6) (3) (3) gular gular Ex. 13 13 z37 SL-1/SL-2 N-5 C-5 W-1 T-top70 A round 70 A 65 A (110) 30/70 (7) (2) (5) top Ex. 14 14 z62SL-2/SL-4/SL-6 N-1 C-3 W-4 T-top 55 A round 55 A 65 A (120) 40/59/1 (7)(2) (5) top Ex. 15 15 z55/z51 SL-2/SL-4 N-3 C-2 W-6 T-top 60 A round 60A 65 A (40/60) 60/40 (6) (2) (5) top Ex. 16 16 z65/z9 SL-2/SL-4 — C-3W-1 rectan- 55 B rectan- 55 B 69 A (100/10) 60/40 (3) (5) gular gularEx. 17 17 z66 SL-1/SL-2 N-5 C-1 W-1 rectan- 55 A rectan- 55 A 67 A (100)60/40 (7) (2) (5) gular gular Ex. 18 18 z16 SL-2/SL-4/SL-6 N-6 C-4 W-4round 55 A round 55 A 66 A  (90) 40/59/1 (10)  (2) (5) top top Ex. 19 19z55 SL-2/SL-4 N-3 C-2 W-6 round 60 A round 60 A 66 A  (80) 70/30 (6) (3)(5) top top Ex. 20 20 z51 SL-2/SL-4 — C-1 — round 55 B round 55 B 67 A(100) 70/30 (2) top top Com. 1 z2 SL-1/SL-2 N-5 — W-1 T-top 100 C round100 C 55 C Ex. 1  (80) 60/40 (7) (5) top Ex. 21 1 z2 SL-1/SL-2 N-5 C-1W-1 rectan- 57 A rectan- 60 A 70 A (80) 60/40 (7) (10) (3) gular gularEx. 22 2 z2 SL-2/SL-4 N-6 C-7 W-4 rectan- 60 A rectan- 60 A 67 A (80)70/30 (10)  (10) (3) gular gular Ex. 23 3 z2/z62 SL-3/SL-4 N-1 C-8 W-1rectan- 62 A rectan- 62 A 72 A (20/100) 30/70 (7) (20) (3) gular gularEx. 24 4 z2/z62 SL-3/SL-4 N-1 C-8 W-1 T-top 75 A T-top 75 A 76 A(20/100) 30/70 (7) (120)  (3) Ex. 25 5 z55/z51 SL-2/SL-4 N-5 C-9 W-2rectan- 55 A rectan- 55 A 70 A (20/80) 60/40 (7) (50) (5) gular gularEx. 26 6 z44/z65 SL-2/SL-4/SL-5 N-1 C-10 W-4 rectan- 60 A rectan- 65 A72 A (25/80) 40/58/2 (7) (10) (4) gular gular Com. 1 z2 SL-1/SL-2 N-5 —— T-top 100 C round 100 C 55 C Ex. 2 (80) 60/40 (7) top Ex. 27 24z23/z55 SL-2/SL-4 N-3 C-11 W-4 rectan- 55 A rectan- 55 A 65 A (10/70)60/40 (7) (40) (2) gular gular Ex. 28 25 Z17/z55 SL-2/SL-4 N-3 C-12 W-2rectan- 55 A rectan- 55 A 70 A (15/70) 60/40 (6) (30) (2) gular gularEx. 29 16 z12 SL-1/SL-2 N-5/N-1 C-13 W-1 rectan- 60 A rectan- 60 A 69 A(70) 40/60 (7/7) (20) (2) gular gular Ex. 30 22 z55/z51 SL-1/SL-2 N-3C-14 W-2 rectan- 55 A rectan- 55 A 70 A (40/50) 40/60 (7) (20) (3) gulargular Ex. 31 3 z17 SL-3 N-5/N-1 C-15 W-1 rectan- 60 A rectan- 60 A 65 A(100) 100 (7/7) (5) (2) gular gular Ex. 32 23 z23/z55 SL-2/SL-4 N-3 C-16W-4 rectan- 55 B rectan- 55 B 77 A (5/75) 60/40 (6) (20) (3) gular gularEx. 33 3 z4 SL-2/SL-4 N-5/N-1 C-17 W-3 rectan- 55 A rectan- 60 A 70 A(65) 60/40 (7/7) (20) (2) gular gular Ex. 34 22 z5 SL-2/SL-4/SL-6 N-3C-18 W-2 rectan- 55 A rectan- 55 A 67 A (75) 40/59/1 (6) (20) (2) gulargular Ex. 35 3 z17/z55 SL-1/SL-2 N-4 C-19 W-2 rectan- 55 A rectan- 55 A70 A (15/70) 40/60 (12) (20) (3) gular gular Ex. 36 24 z68 SL-2/SL-4 N-3C-20 W-1 rectan- 55 A rectan- 55 A 70 A (120) 60/40 (6) (40) (2) gulargular Ex. 37 3 z55 SL-2/SL-4/SL-6 N-3 C-21 W-4 rectan- 55 A rectan- 60 A70 A (80) 40/59/1 (6) (100) (2) gular gular Ex. 38 26 z2 SL-2 N-7 C-22W-3 rectan- 55 A rectan- 55 A 69 A (80) 100 (7) (10) (2) gular gular Ex.39 24 z2 SL-1 N-7 C-23 W-1 rectan- 60 A rectan- 60 A 70 A (80) 100 (7)(20) (2) gular gular Ex. 40 27 z23/z74 SL-2/SL-5 N-3 C-16 W-1 rectan- 60A rectan- 60 A 65 A (50/50) 60/40 (6) (60) (2) gular gular Ex. 41 28z2/z42 SL-2/SL-5 N-3 C-24 W-1 rectan- 55 A rectan- 55 A 65 A (50/40)60/40 (6) (40) (2) gular gular Ex. 42 29 z2 SL-2/SL-3 N-7 C-11 W-1rectan- 55 A rectan- 55 A 68 A (80) 60/40 (7) (100) (2) gular gular Ex.43 30 z2/z15 SL-2/SL-3 N-4 C-12 W-1 rectan- 55 A rectan- 55 A 70 A(50/75) 60/40 (6) (40) (3) gular gular Ex. 44 31 z30/z12 SL-2 N-8 C-24W-1 rectan- 55 A rectan- 55 A 70 A (50/75) 100 (7) (40) (2) gular gular

The symbols used in Table 2 have the following meanings.

The acid generators correspond to those shown hereinabove as examples.

-   N-1: N,N-dibutylaniline-   N-2: N,N-dihexylaniline-   N-3: 2,6-diisopropylaniline-   N-4: tri-n-octylamine-   N-5: N,N-dihydroxyethylaniline-   N-6: 2,4,5-triphenylimidazole-   N-7: tris(methoxyethoxyethyl)amine-   N-8: 2-phenylbenzoimidazole-   W-1: Megafac F176 (manufactured by Dainippon Ink & Chemicals, Inc.)    (fluorochemical)-   W-2: Megafac R08 (manufactured by Dainippon Ink & Chemicals, Inc.)    (fluorochemical and silicone)-   W-3: polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical    Co., Ltd.) (silicone)-   W-4: Troysol S-366 (manufactured by Troy Chemical Co., Ltd.)-   W-5: PF 656 (manufactured by OMNOVA Inc.) (fluorochemical)-   W-6: PF 6320 (manufactured by OMNOVA Inc.) (fluorochemical)-   SL-1: cyclohexanone-   SL-2: propylene glycol monomethyl ether acetate-   SL-3: ethyl lactate-   SL-4: propylene glycol monomethyl ether-   SL-5: γ-butyrolactone-   SL-6: propylene carbonate

Examples 45 to 51 and Comparative Examples 3 and 4

(1) Formation of Lower Resist Layer

To a 6-inch silicon wafer was applied FHi-028DD resist (resist fori-line; manufactured by FujiFilm Olin Co., Ltd.) with spin coater Mark8, manufactured by Tokyo Electron Ltd. The coating was baked at 90° C.for 90 seconds to obtain an even film having a thickness of 0.55 μm.

This film was further heated at 200° C. for 3 minutes to form a lowerresist layer having a thickness of 0.40 μm.

(2) Formation of Upper Resist Layer

Each set of components shown in Table 3 was dissolved in the solvent toprepare a solution having a solid concentration of 11% by mass. Thissolution was subjected to microfiltration through a membrane filterhaving an opening diameter of 0.1 μm. Thus, upper-resist compositionswere prepared. Each of the upper-resist compositions was applied to thelower resist layer in the same manner as for the lower layer, and thecoating was heated at 130° C. for 90 seconds to form an upper resistlayer having a thickness of 0.20 μm.

Resins (SI-1) to (SI-5) shown in Table 3 are as follows.

Molecular weight (SI-1)

15000 (SI-2)

14500 (SI-3)

 9600 (SI-4)

 8900 (SI-5)

10800

(3) Resist Evaluation

Each of the wafers thus obtained was exposed to light with an ArFexcimer stepper 9300, manufactured by ISI, having a resolution maskattached thereto, while changing the exposure amount.

Subsequently, the resist was heated at 120° C. for 90 seconds,thereafter developed with a tetramethylammonium hydroxide developingsolution (2.38% by mass) for 60 seconds, rinsed with distilled water,and dried to form an upper-layer pattern.

The pattern obtained was evaluated in the same manners as in Example 1.The evaluation results obtained are shown in Table 3.

TABLE 3 Composition Evaluation Results Photo- Fluorine- Water acid Basiccontaining Re- follow- gener- com- compound Surfac- Ordinary Immersionceding ing-up Resin ator Solvent pound (C) tant exposure exposurecontact prop- (2 g) (mg) (mass ratio) (mg) (mg) (mg) Profile FallingScum Profile Falling Scum angle erty Ex. 45 SI-1 z2 SL-2/SL-4 N-1 C-1W-1 rectan- 55 A rectan- 55 A 68 A (80) 70/30 (7) (2) (5) gular gularEx. 46 SI-2 z2/z51 SL-2/SL-4/SL-6 N-3 C-2 W-3 rectan- 60 A rectan- 60 A67 A (20/100) 40/59/1 (6) (2) (3) gular gular Ex. 47 SI-3 z65 SL-2/SL-4N-5 C-1 W-1 rectan- 55 A rectan- 55 A 68 A (100)  60/40 (7) (2) (5)gular gular Ex. 48 SI-4 z2 SL-2/SL-4 N-3 C-3 W-6 rectan- 55 A rectan- 55A 72 A (100) 60/40 (10) (3) (5) gular gular Ex. 49 SI-5 z55 SL-2/SL-4N-1 C-4 W-1 rectan- 55 A rectan- 55 A 71 A (80) 70/30 (7) (2) (5) gulargular Com. SI-1 z2 SL-1/SL-2 N-5 — W-1 T-top 100 C round 100 C 55 C Ex.3 (80) 60/40 (7) (5) top Ex. 50 SI-1 z2 SL-3/SL-4 N-1 C-8 W-1 rectan- 55A rectan- 55 A 68 A (80) 30/70 (7) (50) (5) gular gular Ex. 51 SI-4 z2SL-2/SL-4/SL-6 N-3 C-10 W-2 rectan- 60 A rectan- 60 A 67 A (80) 40/59/1(6) (5) (3) gular gular Com. SI-1 z2 SL-1/SL-2 N-5 — — T-top 100 C round100 C 55 C Ex. 4 (80) 60/40 (7) top

It can be seen from those results that the resist compositions of theinvention are excellent in profile, unsusceptibility to pattern fallingand scum generation, receding contact angle, and water following-upproperties with respect to each of ordinary exposure, immersionexposure, and multilayered resists.

The invention can provide a positive resist composition which issatisfactory in pattern profile, pattern falling, and scum performance,is excellent in the receding contact angle of an immersion liquid, andis suitable also for immersion exposure. The invention can furtherprovide a method of pattern formation with the composition.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

What is claimed is:
 1. A resist composition for ArF exposure comprising: (A) a resin which comes to have an enhanced solubility in an alkaline developing solution by an action of an acid; (B) a compound which generates an acid upon irradiation with actinic rays or a radiation; (C) a fluorine-containing compound containing at least one group selected from the groups (x) to (z): (x) an alkali-soluble group; (y) a group which decomposes by an action of an alkaline developing solution to enhance a solubility in an alkaline developing solution; and (z) a group which decomposes by an action of an acid, and (F) a solvent, wherein the resin (A) has no fluorine atom and the fluorine-containing compound (C) is a resin containing a repeating unit represented by the following formula (C4):

in the formula (C4), X₁₁ represents an oxygen atom, R₁₁'s each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may be linear or branched and may have one or more substituents, and R₁₂ has a structure represented by formula (F3):

wherein R₆₂ and R₆₃ each independently represents a fluoroalkyl group, and R₆₄ represents a hydrogen atom.
 2. The resist composition for ArF exposure according to claim 1, wherein R₆₂ is a trifluoromethyl group.
 3. The resist composition for ArF exposure according to claim 1, wherein R₆₂ and R₆₃ are a trifluoromethyl group.
 4. The resist composition for ArF exposure according to claim 1, wherein the fluorine-containing compound (C) has a molecular weight of from 1,000 to 100,000.
 5. The resist composition for ArF exposure according to claim 1, wherein the amount of the fluorine-containing compound (C) is from 0.1 to 5% by mass with respect to the total solid components in the positive resist composition.
 6. The resist composition for ArF exposure according to claim 1, which provides a film with which water has a receding contact angle of 70° or larger.
 7. The resist composition for ArF exposure according to claim 1, wherein the total solids concentration in the positive resist composition is from 1.0 to 6.0% by mass.
 8. A pattern forming method, comprising: forming a resist film by the resist composition for ArF exposure according to claim 1, exposing the resist film; and developing the exposed resist film.
 9. The pattern forming method according to claim 8, wherein the resist film is exposed to light having a wavelength of from 1 nm to 200 nm.
 10. The pattern forming method according to claim 9, wherein the exposing is an immersion exposure in which the resist film is exposed to light through an immersion liquid.
 11. A method for manufacturing a semiconductor device comprising the pattern forming method according to claim
 10. 